HP500EFI problems

[RickSE]

I thought I had this problem fixed but it has re-appeared.

My motor runs great below 4500RPM's, good power and all seems normal. When I lay into it though with a fully warmed up motor it will run fine for a few seconds then starts cutting out, >4500 RPM’s. It will loose RPM's then kick back in; loose RPM's then kick back in. It won't recover until I pull back on the throttle, then it runs fine unless I go above 4500 RPM’s again.

This appeared this year after the winter lay-up. Over the winter I changed the main fuel/water filter, oil and spark plugs. On the first trip out I concluded it must be a fuel supply problem. I lifted the hatch after one attempt to run under full power and could hear the fuel hissing or boiling near the EFI booster pump filter. Thinking the filter may be clogged and tried to replace it at the lake but no one had the correct filter. While looking for the filter a Merc tech told me I probably had trapped air in my fuel system since I didn’t fill the fuel/water filter with fuel when I replaced it over the winter. This seemed to make since, the trapped air was being pulled into the booster pump when I hit the power and would cavitate the booster pump, vapor locking the motor until I got out of the power. He suggested I drop my fuel/water filter a make sure it was full. We went back to the boat, reinstalled the old booster pump filter since I couldn’t find a replacement and headed back to camp to check & drop the fuel/water filter. On the ride back the boat ran great, full power and no more vapor lock problems. The boat sat for about an hour with the booster pump filter removed so I figured this must have purged the air and all was good.

Wrong, about a month later I tried running the boat hard again and the loss of power is back, same as before. I’ve since dropped the fuel/water filter and it’s completely full, no air trapped in there. 500’s are not common in my area so I’ve yet to replace the booster pump filter, but will order one today.

What is going on?
Do I still have air trapped in the system?
Am I sucking air into the fuel system from somewhere?
Is my booster pump filter clogged?

The motor has 65 hours. Plugs look good and are the correct NGK part number. I’ve yet to check the cap and rotor but wouldn’t think they would go bad with only 65 hours.

This motor has a mechanical pump which pulls fuel from the tank through the fuel filter/water separator. The pump supplies fuel to the booster pump and fuel cooler, which in turn pressurizes fuel through the booster pump filter and to the fuel rails.

[Bad-Tat]

Joe P had a similar problem with his and it ended up being the pickup unit in the dist. It didn't show any fault on the fancy test unit either.

[Mr X]

Rick, as funny as it sounds...........check all the wires on the back of the tachometer, make sure they are snug and not shorting against each other. We had a 28ZX that had the exact same problem.......and thats what it was.

[roadtrip se]

Another quick check is your flame arrestor.
If it's dirty, it could be choking your air flow at higher rpms.

Also time for a scan of the ECM.

I'll also take a peek tonight at my service manual.
If I find something there, I'll post it.

Good luck figuring it out.

RT

[RickSE]

I'll check the tach connections tonight.

I cleaned and re-oiled the flame arrestor in May before the first trip. I'll check and make sure I didn't over oil the element.

When it cut out on me Sunday it began to misfire and then backfired through the intake before I backed off. The boat accelerates great just seems as though it can't maintain big power for anything other than short bursts before it either runs out of fuel or ignition.

I still suspect fuel since the problem temporarily went away after I pulled and reinstalled the EFI filter. Especially since it accelerates fine but seems as though it can't maintain a good fuel supply at WOT. I ordered a new EFI filter today and will also change the fuel/water sep. filter.

My biggest problem now is that there's no one in my area who can service this motor. There are two Merc shops in Flagstaff and neither one has the correct stuff to scan a 500. Phoenix or Havasu are my next closest options if I have to go that route.

Roadtrip, is the service manual worth it? I've still yet to buy one.

[BUIZILLA]

What's the fuel pressure reading?

JH

[Dr. Dan]

:eek!:
What's the fuel pressure reading?

JH

I am with Jim...last year I had a totally Random Fuel Supply Problem ...when we lost everything...turned out the Main Fuel Shut Off had vibrated to the Off Position... I am never even in that area...but when we opened up the access plate...there it was. We poured gas into the Fuel Filter, and lines...and it ran again...boy did I feel stupid...but I was glad too...that it was soo simple.

Brad has a similar problem to yours, except his stops at about 40 mph, or when he hits a wake, with his 502 EFI and is going thru a diagnosis procedure currently. Starting with injectors and working backwords from there.

Hope ya find it Rick... I am sure its gotta be something fuel or spark related...possibly something is jammed in a line? Dirt or foreign object? But it would not explain the consistency in the RPM miss?

Hmmm ... ???

Doc :spongebob

[roadtrip se]

after looking at it...a couple more things to check...

-Water in gas, old gas, or just cheap gas. I run 89 octane.
-Check for restrictions from the engine forward all the way to the tank vent, including the vent loop, shut-off valve, and entry points under the decking.
-Check all vacuum hoses, spark plug wires, and connection to distributor.
-Verify all spark plugs are in the hole and gapped at 35.
-Check distributor for salt damage, the boat came from Port Aransas on the Gulf.
-Check advance on throttle body linkage.
-Check ECM grounds and sensors for cleanliness and good connections.
-Fuel pressure regulator. Pressure should be 43psi.
-Check fuel return line from pressure regulator to water seperator filter.
-Fuel pump noise, failing?
-Injector test.

Again, it's probably something very simple.

Good luck,

RT

[Lenny]

Todd, fogive my stupidity, BUT, 43 PSI on the fuel ??? I thought it should be about 7... :confused:

[DonCig]

Rick, I just purchased the Merc video series of tapes on working with EFI engines. I had a similar problem with my 502 MPI last week. I will call you to discuss.

Don

[Dave_N]

Another possibility is that you are hitting the rev limit. When the the ECM enters Engine Gaurdian mode the Available Power will be reduced to 90% and the rev limit will drop to 4500 RPM. When this happens you should hear a two beeps per minute alarm. This can happen without alarm if the ECM thinks the gear shift is in neutral.

Dave

[RickSE]

Thanks guys,

I checked the tach. All the wires and connections going into the tach seem fine. If the problem persists I'll disconnect the tach.

Found a semi loose connection on the ignition switch. I don't think it was loose enough to cause the problem but hard to tell, it's tight now.

Pulled the plugs. All look normal for a 500 running at 6000', sooty with tan porcelain tips and wet/oily threads, except #2 & #4, both had dry threads with light grey electrodes. The motor was running at a slow speed cruise and idle though before being shut off.

Flame arrestor looks ok, clean and not over oiled.

Forgot to check the fuel tank shut off valve last night. :rolleyes:

Can’t be on the rev limiter @6000’ w/25P, cutout hits long before the limiter should be kicking in. It will run fine for 30 seconds at +4500 RPM's then start to loose power and fall back.

I’m running 87 which should be good for my elevation. Just put 40 gallons of new fuel in last week before talking it out last Sunday. It had a hint of cutout 2-weeks ago before I put the new fuel in but I was not running it hard.

I can hear the booster fuel pump is coming on.

New fuel filters will go on as soon as they arrive and I’ll check all lines for restrictions, then take it out again.

Also need to order a manual. I assume there is a procedure to check fuel pressure with an analog gauge, not scan tool.

[RickR]

Rick
I have not worked on a EFI Merc but,

You should be able to find a universal fuel pressure gauge and adapters at your local auto parts. Make sure you have an adapter that will fit the Merc fitting, which should be on the fuel line between the booster pump and injectors. GM uses a valve that looks like a Shrader (air) valve.

[RickSE]

Thanks Rick.
I think your right, looks like the Merc parts breakdown shows a Schrader valve on the starboard fuel rail.

500EFI Fuel Rail Ass'y. (http://www.mercruiserparts.com/Show_Pictures3.asp?dnbr=884709&ivar=images/CRUISER/884709/A32.png&inbr=7595&bnbr=110&bdesc=FUEL+RAILS+AND+INJECTORS)

[GEOO]

Did you change the fuel filter after the 2nd pump near the fuel rails?
Rick has a good idea, put a fuel pressure gauge on the fuel rail Schrader valve. The only problem I have is getting some one to ride in the back and check the pressure.

[RickSE]

Geoo,
A new filter is on it way. I've never changed the second filter and am pretty sure it's the original unit put on by Merc. I really suspect it's the filter or air still in the system especially since I heard what sounded like fuel boiling at the filter when I shut the motor down immediately after it cut out on me in May. The noise was pretty loud and slowly went away as the motor sat giving me the impression it was vapor locking for some reason at the second filter.

I didn't change the filter right away because the problem seemed to go away after I removed, drained and reinstalled the second filter while looking for a replacement at the lake.

Oh well, if this is it I should know next week when the filter gets here. Sucks to live where you’re surrounded by aluminum fishing boats and canoes. Not many 500's around here, which makes it hard to find parts and service.

[SPSU Z25]

We have an '89 Z25, the engine ran fine for several weeks after being de-winterized. Pulled 4,400 rpm wonderfully, then one week it would not go above 2,600 rpm. We changed the spark plugs, nothing happened, the coil didnt do anything either. It was the points in the dist that were almost closed. The engine did not have enough power to make any more rpm's.
Is the ignition in good shape?

[RickSE]

Man-o-Man,

How hard is it to get a fuel filter?

Apparently the filter I need is on backorder with Merc. I ordered the filter a week ago and I'm told it will take probably another week to get one.

Anyone have a source for this fuel filter?

Merc. #35-807174T

[RickSE]

Nevermind.

Found some in Phoenix.

[farmer tx]

Rick do you still need a #6 500 EFI manual?

[RickSE]

Farmer tx,
Yes I still need a manual. Do you have one?

Haven't you mentioned coming over to Powell in the past? Any plans to do so?

[farmer tx]

You have PM

[RickSE]

Well two new fuel filters and the problem still exists. I also ran a gallon of fuel through the system with the electric pump to try and purge any air and it's still crapping out on me at high RPM. It cut out so hard yesterday that it threw everyone in the boat forward, almost like turning the key off at 5000 RPM's. This can't be good on the drive.

Anyway I'm done with it. This thing is still under Merc. & Donzi warranty so it's going in for service. Now the biggest challenge, finding someone qualified and someone I trust to work on it. :frown:

[RickSE]

Man I hate to give up so since I can't get the boat in for service until Aug. 8th I started looking into a few things last night.

I pulled the fuel tank vent hose off the bulkhead fitting and checked the hose and fitting for blockages. Both seemed fine and I was able to blow air through the fitting and also through the hose into the tank once I cracked open the gas cap. No restrictions here.

I disconnected the outlet line from the mechanical fuel pump and ran it to a catch can; also disconnected the elec. fuel pump & killed the ignition. Was surprised to find this line essentially dry with no fuel in it after running the boat two days ago?? I then cranked over the motor. All seemed fine and the mechanical fuel pump is working. Not sure what kind of pressure it is building but it is working. I think I’ll install a fixed mount gauge on the second outlet from the water separator for kicks. Although the elec. pump may negate any pressure built by the mech. pump.

I pulled the flame arrestor to clean and rinse the element. It's now drying and I'll lightly re-oil it before re-installing. I was concerned that I may have over oiled the element last winter, but I don’t think this would have caused the vapor lock.

I checked the outlet line from the water separator to make sure it's tight. The line was a little loose but I'm afraid to over tighten due to the fact that the housing is aluminum. I'll probably pull this line and reseal with thread sealant this weekend; also check for restrictions in all the lines from here to the fuel rail.

I believe my last and final check will be to pull the fuel cooler unit and check the o-ring on the inlet line to the elec. pump. I just want to insure that I'm not pulling air into the system between the mech. & elec. pump.

I probably should also consider pulling the tank pick up unit to check the pick-up line and also check the hose from the tank to the mechanical pump for restrictions.

I checked the fuel shut-off valve the other day and it's fully open.

If this doesn't fix it then I'll really give up and wait until the 8th when a pro can look at it.

Anyone know where my oil temp should be running? Seems to run cool, around 140-150 while cruising and bumps up to 180-190 when I stop and idle, Valvoline Racing 40W. The 500’s are supposed to have a thermostatically controlled oil cooler. Just seems like it is running cool when the engine is warmed up. Engine water temp is normal 160-180. I know for a fact that this motor will not run hard if it’s cold. Just concerned that running in cool (60 deg.) water at high altitude may be contributing to the problem.

[BUIZILLA]

What's the fuel rail pressure?

[RickSE]

What's the fuel rail pressure?

I don't know. I don't have a gauge for the fuel rail and have not pursued this since it really needs to be checked under load. I'll probably leave this to the shop since they have a dyno and can run the motor under load without going 70+ MPH.

I'm sure it's loosing pressure since I've heard it hissing or vapor locking fuel in the line between the elec. pump and fuel rail. So my main question now is why is it vapor locking? Blockage, suckin air, failing pumps??

I just want to make sure I look at everything I can hoping that I can either fix it or shorten the amount of time it's in the shop.

[Dave_N]

For clarification "vapor lock" is caused by fuel boiling (heated to the point that it goes from liquid form to gas form) in the fuel system. The pumps can't pump fuel in a gas state. Fuel under pressure takes a much higher temp to boil. It would take very high temps to boil the fuel in the line between the pump and fuel rail, as it should be pressurized to around 40PSI.

You may have a fuel restriction, but even given the high elevation, I don't think your problem is vapor lock.

Dave

[Rootsy]

one last thing to check before you tow her off... make sure your battery cables are TIGHT on the battery terminals and load test both batteries (why do i assume you have two????, but anyway)... also, make sure the cables are tight at the starter (or junction where the main hot feed for the electronics joins the cable) and the grounds are tight on the block... went through this on the 16.. same thing... suddenly gain or should i say lose 400 - 500 rpm and then it'd mysteriously come back and then go and come back... battery cable was loose on the hot side of the battery... not much... you could just rotate it under the wing nut... it started fine, idled fine, ran mid range fine... WOT was the only place there were any issues... who woulda thought...

JR

[RickSE]

The boat ran fine last fall before winter lay-up. I did six things over the winter. First run out of the box this Spring and I have problems on a motor with 64 hours on the clock.

Changed the oil.
Changed the drive lube.
Changed the water separator but did not fill new one w/fuel.
Changed the Spark Plugs with the same NGK plug number that came out at correct gap.
Cleaned and re-oiled the air filter.
Replaced both batteries w/Optima’s.

So did one of these things cause the problem??

Engine & drive oil can't be it.
I just changed the water separator again and fill w/fuel.
I'm currently running the original set of plugs and have had the same problem with both sets.
The air filter is currently being cleaned and re-oiled again.
Rootsy, I will check the batteries. Maybe I should stick the old batteries back in. :bonk:

If I over-oiled the air filter and its restrictive wouldn't this cause the manifold vacuum to go up at high RPM and in turn cause the fuel pressure to drop? I'm really diggin for stuff now.

[RickSE]

Rootsy,
You may be on to something. I checked the battery cables last night. 3 of 4 cables were not tight, like you describe, the wing nuts were snug but I could easily rotate the cable when I grabbed the wire. They are TIGHT now. This also made me think about what has happened so far. On the first trip when the boat crapped out I was running on one battery. When I pulled off the fuel filter at the lake I turned the batteries off and upon restarting may have switched to the other battery. This is when the boat ran fine and the cutout went away. I'm not sure which battery I've been running on lately but if it were the cables then I know which battery was causing the problem.

I also checked the fuel pressure from the mech. pump, 5psi from cold cranking with the elec. pump off.

The line from the water separator to the elec. pump is clear and tight, no obstructions.

I also noticed that the AC recharge hose I have, which is pretty long, has the correct schrader connection for the fuel rail, just need to change the gauge. If I still have problems I'll use this to check the EFI pressure.

I’ll know in a few days.

Thanks guys.

[RickR]

Rick
If your helper does not want to ride holding the hatch up to read the fuel pressure gauge, remove the hatch.
3 machine screws and 2 clips, she's off! I use black tape to hold the struts.

[RickSE]

One EFI fuel gauge ready to go, hatch removal not required. Someone should be able to sit in the back seat and view. 45 PSI with the key on, engine off. I'll try it tomorrow under power. Just need to tie down the hose.

[BUIZILLA]

Idling, in gear, should be about 35-38, full throttle about 43-45.... if it creeps higher, then your little mickey mouse screen in the fuel cooler log is plugged up. I fought this malady for 4 months.....

JH

[RickSE]

Buizilla,
Where is the screen? In the fuel line or in the water line part of the log?

[RickSE]

Screw work!!

Heading out now to run the boat. I should have results in an hour or so.

Poodle, Are you saying the regulator could be bleeding air into the fuel system? Regulator is on the pressure side of the pump though.

We'll see what the fuel gauge says. If the fuel pressure drops then I'll have to wait for the shop to fix under warranty.

[Jamesbon]

Hmmm, speaking of batteries, we had a similar problem with a late model Cobalt. She ran great up until 4200 rpm, then cut out like she was hitting the rev limiter. After much work, the mechanic swapped out the batteries for new ones and she ran like a bat outta hell. Apparently those EFI motors are very sensitive to your batteries condition.

Good luck!

[RickSE]

Speaking of Bat Outta Hells, my Bat seems to be back from Hell. :beer:

We went out to the lake with tight battery cables and a fuel pressure gauge. Put the boat in the water and the fuel pressure gauge stopped working. About the time it stopped working the sky opened up, rain, hail, lightning, wind and a 10-15 deg. temp drop. Pulled the boat out and waited it out in the parking lot for about an hour. Fixed the gauge and put the boat back in the water. 38-40 psi at idle, 40-42 psi past idle to 4800 RPM's. Pressure bumps up when I accelerate then settles back down to 40 or so. The fuel system seems fine and I really believe the problem was the battery cables. The only significant changes I've made since it cut out on Sunday are tightening the battery cables and cleaning the air filter. Funny that the guy riding in the boat with me had the same problem on a boat years ago.

Anyway we ran the boat pretty hard and everything seems to be back to normal. That's if 4800 RPM's, 71-MPH on the speedo, @6500 ft. elevation with a lab finished 25P Mirage+ is normal. :hyper: Man I love this boat. There's a 55-MPH state highway running adjacent to the lake and we were passing the cars on the highway. :eek: Too funny.

Thanks Rootsy & all

Off to a lower elevation lake I go.

[Jamesbon]

Great news RickSE!

Sometimes the most mundane problems are the hardest to diagnose.

Glad to hear she's screaming again! Nice, very nice Classic, by the way!

[roadtrip se]

I knew it would be something simple...

Ran into this too on an earlier ride.

Sorry I didn't point it out on my check list...

[RickSE]

It’s ..........back

My problem from last year appeared again on my first trip out this year but this time with a new twist. Again last year my motor would cut out at high RPM's under load, above 4,000 RPM. I originally thought it was fuel delivery, maybe air in the fuel system from when I changed the fuel filter/water separator; cavitating the booster pump. After trying several things I finally came to the conclusion that it was my battery cable connections being loose that caused the cutout problem. The day I tightened the battery cables and ran with a fuel pressure gauge the problem went away and the boat ran fine all season long.

Now jump to this year. As usual I changed my main fuel filter/separator after the winter break, filling the new filter to the top with fuel to avoid problems. I took the boat out this weekend and it started acting up again. It acted up on battery #1 so I switched to battery #2; the problem went away so I assumed the connections on battery #1 might be loose. Now for the new twist, later in the day running on battery #2 the motor started cutting out at cruise, 3,500 RPM's. I pulled in and spent some time on the beach and then headed back out for another bay. I idled the boat out of our cove for a few minutes then went to get on plane, the motor backfired and died. I spent the next 10 minutes trying to get it restarted. It would restart then immediately die, no idle. I couldn't get it to run so I got towed back to the beach. I then did the following,

Removed the freshly cleaned and oiled air filter and left it off.
Cleaned and retightened all the battery cables.
Removed and cleaned the distributor cap.
Checked the wiring on the back of the motor.

After about 30 minutes I restarted the motor with the air filter off and it ran fine. I ran it in the cove for a while, then put the air filter back on and took it out for some high speed test runs. No problems what so ever running hard at 5,200-5,300 RPM and the boat ran fine for the rest of the weekend. Found out my speedo tube blows off past 75-MPH.

Anyway sorry for such a long write up but my main question is have you other 500EFI guys, with the two fuel pump set-up, ever had this problem after changing your fuel filter(s)? When you change your fuel filter(s) do you do anything special to purge air out of the system? I'm assuming from the way mine was dieing at idle on Saturday that there is more to this then loose battery connections and since it always seems to happen after I change the fuel filter that it is related to air in the fuel lines.

I'd appreciate any feedback anyone may have. I'm also going to call now Merc. for tech support.

Update,
I just talked to Merc. Racing Tech Support. They said air in the fuel line should not be a problem, any that got in there will just purge out through the injectors. We talked about the batteries and alternator output, I seem fine there. Their main concern was my fuel quality, maybe water in the tank, especially since I had just topped-off the fuel tank on Saturday before it started crapping out on me. Merc. suspects that there may be water in the tank that got stirred up when the tank was filled up. they are suggesting I check the fuel in the tank.

[cigarette30]

Rick,
I really think you will find it to be electrical. I have even had problems exactly like yours if one battery is real low, and the selector switch not set on both. Also, if the batteries were changed without the correct ampere (not in your case), and loose connections have also produced your symptoms. Good luck, personally, I am still not sold on the infamous "blue motors" yet. Header replacement, and head/valve spring problems are a bite for a $25,000 motor.
BTW, if the problem persists after being run and hot, look at vapor lock, and one of the two pumps. Thats why merc. added the second in 2002.

[Avialanche]

Does your boat have a Crank Position Sensor? the 2004 and earlier big block gmc/chevy trucks(not sure if same parts are used by Mercruiser) have earlier sensor design, which warps after a bunch of heat cycles, thus pulling sensor away from the trigger wheel and it will miss the trigger signal more likely at higher rpms and then when engine cools off, sensor resumes it's original form, and when you improve battery connections, improved current flow & voltage could increase the sensor's sensitivity and make this problem go away for awhile, but the older the sensor gets, the more it warps...........i've seen threads about this at chevy truck/gmc sites & clubs. The CPS sensor has been redesigned to resist warping.

[Dr. Dan]

:spongebob Rick...I have not had any Gremlins in my set up...I will be speaking to my Engine Builder over the next week or so...I will see what he thinks. Ya gotta get a GPS SPeedo....it's a fun toy for those Speed Obsessed.

BTW I change my batteries every other year or each year...after Brads did a ShotGun Explosion in his X-18... if anything it pushed me to changing them annually. I run on the "Both" selector...switch. But I have run on either 1 or 2 before and no issues.

Before Cumberland I did find the Cables were in fact loose on both Batteries and I tightened them puppies up...which is a Major PIA if ya have the Bling Boxes with the Steps(Covers)....ya have to be part part heart surgeon to get in there.

I will let ya know what I find out if anything...:smash:

Doc :beer:

[RickSE]

Avialanche, No crank sensor, it's a distributor motor.

I'm wondering now if I may have more then one thing going on. I'm pretty sure the high RPM cutout is related to the battery connections. Especially since it seemed to go away last Saturday morning once I switched from one battery to the other.

I'm really wondering if Merc. is right and the crap that happened Saturday afternoon is related to water in the gas, especially since the Sat. afternoon problems started right after I got gas at the marina? Wouldn't the following make sense?

So I top of the tank with 30 gallons of fresh fuel. If there was water in the new fuel the boat would run fine for a while since the water and fuel would be stirred up for a while after being dumped into the tank. It wouldn't start running bad until the water had a chance to settle to the bottom of the tank and hit the fuel pick-up. Towards the end of the run back to camp, 20 minutes after fueling the motor started acting up but got us back to camp, waves and bouncing would have kept the fuel semi-mixed. The boat was then parked and sat for 1-2 hours before we headed out again, giving any water in the tank plenty of time to settle to the bottom. After sitting we fired it up and idled out of the cove, long enough to consume the existing fuel that was in the system from the filter up. After consuming this fuel, which was probably still good with minimal water, it began picking up water from the tank and killed the motor. It then ran like crap until I was able to cycle whatever water that was in the system through the motor and it began picking up good fuel again. Once we pulled it back to the beach and re-fired again 20-30 minutes later it ran great and never had the problem again. I know I cycled a lot of fuel through the motor while we were floating trying to get it restarted.

Not that the boat has sat for a while I'll pull some fuel out of the tank with the pump and see what it looks like. Also in light of what is being said on the other post about Quicksilver filters/separators being crap I'll probably install a Racor filter on the motor before heading out again.

[Mr X]

Why not just take in to a Mercury shop that has the Mercscan tool? :idea:

[RickSE]

Why not just take in to a Mercury shop that has the Mercscan tool? :idea:
That's a good idea but................the closest Merc. shop that can scan my motor is in Phoenix or Havasu, a 2 1/2 to 3 hours drive one way and my dad's shop is 5-hours one way. Almost all have a one month waiting list this time of year and I'd have to leave my boat there for who knows how long :frown: . This boat doesn't go anywhere unless I'm with it. I almost took it to the Formula dealer in PHX last year to run on the dyno but the problem went away so I canceled the appt. The two local shops don't have the software for the HP motors and one doesn't even know what a 500EFI is. Heck no one even has the filters in stock; I had to order them last year from the Formula dealer and this year from Poodle. :embarasse If the problem persists I'll see about getting it scanned but I'd be surprised if it told me anything more then maybe low fuel pressure.

I wish it wasn't this difficult since a scan should only cost $30-$40 but now add on $100 worth of truck fuel to get the boat down and back up the hill.

[cigarette30]

Rick,

Join the club, fun huh? I am in the same "boat" times 2. So frustrating, closest dealer 2.5 hours, 3-4 weeks, get home, another problem. Hey, thats why I have two boats, and people say I am crazy, no, I just know 1/2 the time one's down.

Anyway, you indicate the problem went away once when you changed your battery switch, mine did the EXACT same thing, had a bad cell in that battery. If it was a fuel problem (although I agree, maybe a combination) sure seems to favor when you have worked on the electrical side. On another note, and don't get me wrong, the "Registry is the best", but may I suggest posting your question on OSO, there are hundreds of 500 efi's, compared to a few, and even a search may help you.

[roadtrip se]

Last run of the season in 2005, my tachometer went completely crazy.

I went back to the barn and checked and tightened every negative I could find, including the battery posts. Shake down run in early May and the problem was gone. 500's do seem to like clean power.

Your stuttering and cut-out problem does sound like classic bad gas.

Don't give up the faith, I have had two sets of 500's plus the one I have now, and besides the occassional small problem, they have been flawless. Julie, the prop goddess at Throttle Up, tells me that most race boats that they scan with this package have run hundreds of hours at mostly full throttle and they just don't break.

I'm with Ted, your boat needs to go to the shop for a scan, if the problem continues. I wouldn't let it ruin my summer.

[RickSE]

I just called Sun Country in PHX, said he's booked until June 21st and requires an appt. for a scan. :embarasse We chatted a little about my problem and he suggested I change the fuel filter/separator again and check the fuel. He said if I still have problems to call him back and he'll work me in. Shoot the scan only takes 15 minutes, easy money. :boggled:

I searched OSO pretty hard last year. Most of the similar problems I read about were related to the older 500EFI's with the single fuel pump. I thought about posting on OSO but have to re-register since the last time they changed the board around.

Once the filter/separator fills up with water won't it just bypass and let the water go to the engine? I was thinking about cutting open my filter when I take it off to see if any water comes out the bottom.

Thanks guys.

[Formula Jr]

Have you tried swapping the coil? I'm just trying to think what could explain ALL of the symptoms here. An arching coil could explain most of it. It seems to be both tempurature related and electrical.
But I can't explain why it would run all day somedays and not on others.
This one is baffling.

[Dr. Dan]

:spongebob Well... I feel for ya in the "Long Drive Dept." when I did the repower.... the Boat was 4.5 hours one way away from me...it took alot of Logistics to plan all I had to accomplish when I went there...but guess what...the guy knew his stuff...the Boat Runs like a Scalded Dog...just ask Todd or anyone who was at Kentucky!

So I am with Ted...take it to where they know their stuff...and get your ass back on the water....with a correct running boat....I don't have the patience... if its broke it gets fixed , replaced or sold....or I get a new toy...those are my options.... otherwise I don't boat.

Real curious to see what they say.

Good Luck Rick!:beer:

[LKSD]

Fuel Psi regulator on the fritz????

[BUIZILLA]

Does the 500EFI have that little screen in the fuel cooler return fitting??

[LKSD]

If you can get me an engine serial # I can check that particular engine's fuel system for screen and parts diagram. I dont remember off the top of my head. Let me know. Jamie

[RickSE]

Motor is OM053572. This should be the fuel cooler diagram. Fuel Cooler System (http://www.mercruiserparts.com/Show_Pictures3.asp?dnbr=884709&ivar=images/COMMON/9918.png&inbr=7595&bnbr=120&bdesc=Fuel+Pump+And+Fuel+Cooler)

I pulled the fuel filter last night, put a new one on and checked for water; no water currently in the fuel but then again it was running fine when I pulled it off the lake on Sunday. For kicks I cut open the filter/separator to see what was inside. There certainly is not much to these Merc. filters.

Anyone know why there are two fuel regulators on these motors? The second regulator at the end of the fuel rail doesn't seem to do much, no bypass.

I must state though that this motor ran fine for 30 hours last year after the initial problem went away, not one hick-up for the rest of the season. Now just like last year, after the winter lay-up it hick-uped again. Nothing changed over the winter accept the batteries were disconnected, filters and oil were changed and it sat with a full tank w/stabilizer.

I really believe my prior assumption is correct. The high RPM cut out is a battery or battery connection problem. The no idle problem I had was due to water in the tank after I filled up at the lake and the boat sat for a couple of hours allowing the water to settle in the tank. After cutting open the Merc. filter I really believe there is no way in hell this filter can keep water out of the motor if you suck up fuel with a high concentration of water.

Will the Racor filter do a better job of keeping water out?

Thanks again guys, I really appreciate all the comments and value every one.

[BUIZILLA]

Rick, I truly hope it's not a clogged return screen, item #16.... my Formula did the same ****, and it took me 5 months to finally figure it out, as the screen was buried in the cooler fitting under the regulator, and it was mostly plugged. It is a mutha F***** to get to... It all started because of those crappy, and I emphasize CRAPPY, Merc filters. We get injectors for these in my shop every week to be cleaned, due to these filters being junk. I'm NOT exaggerating when I state EVERY week, just recently for both Carrera, and Pantera Boat Co's.... you don't need the return screen if you use the RACOR filters...

I had more blood in the bilge than water, just ask Poodle what I went through...

The RACOR replacement will do a great job. Your engine will thank you...

Jim

[RickSE]

Thanks Jim,
I've read small bits of your ordeal before but have never heard the entire story.

Just for kicks I called the two local guys to ask again about scanning my motor. The first guy is not Merc. certified but said he thinks he can scan my motor. I'll call him back next week and see if he can work me in for a quick scan. The second shop which used to be but is no longer Merc. certified told me he can scan Mercruiser but not Mercury Racing. I told him my I have a HP motor that says Mercury Racing Mercruiser on it :yes: . He insisted that if it's a sterndrive he can scan it. I then told him I'd like to bring it in and wait while he scans it and not drop it off for a later pickup. I then got to listen to him and his mom argue about this over the phone, "he doesn't want to drop it off"......."well I'll have it done in a day"....."I know but he doesn't want to drop it off". My response was "OK, thanks, I'll call you back". You know, I don't want to be anal but it's my boat and I'm gonna be anal. Some people just don't understand, this isn't an aluminum fishing boat. I go where it goes.

So scanning seems to make sense if I can get it done locally. I was told though that Merc. does not sense or store fuel pressure with the computer. This is the same guy though that told me the Merc. fuel filter/separators are the best filters in the world and will not let water through. I'm not sure I believe that yet.

[BUIZILLA]

Rick, I don't want to derail your thoughts that it could be ignition as well, I'm just relating common fuel issues... mine had the same sporadic high speed miss, it ended up being 1 bad injector, the scanner missed it twice as it doesn't load balance the engine to detect a bad injector... I put all 8 injectors on a injector test bench and found the bad one right away, it had trash in it that the Mouse House filter didn't catch... I fixed that anomaly and the engine still was sluggish at times, not all the time... :splat: :bawling: sometimes shutting off totally without warning... get yourself a GOOD fuel pressure gauge and tap into the fuel rail schrader valve, the gauges are cheap and can be bought at most auto parts stores... fuel pressure should be 35-36# at idle, then disconnect the vacuum source hose from the UPPER fuel rail regulator/damper and it should rise to 42-44#, if it's above 46 or so, the bastard screen is restricted, mine was 56-60# before I finally fixed it... the more return restriction, the higher the rail pressure. These engines are VERY fuel pressure sensitive, since they basically run in an open-loop fashion. Without an ego sensor, there is no fuel map correction predictability for fuel pressure issues...

Now, as far as ignition worms...

JH

[mrfixxall]

Rick,,i had the same problem last year on one of my cust boat....it ended up being a loose fuel line before the fuel seperator....it wouldnt leak it would just suck air and not fuel....the way i found it when it starting acting up and then finally the motoe would quit so i spun off the fuel filtr and it was dry...
good luck.

[RickSE]

So I now know what the problem is I just don't know what is causing it. :confused:

I put a Gaffrig electrical fuel pressure gauge on the dash so I could watch the fuel pressure. The fuel pressure is rock solid until it begins to have problems then it starts to drop. If I don't let off the throttle the pressure will drop to zero then back up, zero than back up. When I got back from the Powell Gathering I called Merc. Tech Support and explained what is going on. I was told the mechanical pump spec. is 4-7 psi, electrical pump is 38-40 psi, electrical pump should spike to 100+psi when I plug the regulator bypass.

My mechanical pump pressure rarely goes above 4psi. The electrical pump pressure is 38psi and bumps to 100psi with the regulator bypass plugged.

The tech guy asked if my electrical pump had ever been run dry and stated my mech. pump is on the low end of spec. He said my elec. pump could be going away. When I asked if the elec. pump could be getting hot and vapor locking the fuel he said, "no, the fuel will cool the pump". Other then that he gave me no more hints.

On a whim I changed the EFI fuel filter on the back of the motor and took off for Havasu and low elevation figuring this would be a good test. I ran around with Thriller, Yeller & Fegettes and the boat ran like a champ. I was nervous since I'd never run the boat below 3,600' but had some pretty hard extended runs above 5,000 RPM. I thought ye-ha it's fixed, then on the last run of the day it did it again. I let off, idled a little then got on it again and it was fine. :confused: Even though it hick-upped again it seemed to be a lot less severe. I honestly believe it is vapor locking and changing the EFI filter was enough to help it along a little further, but there still is a problem somewhere. I thought about it on the way back home, 3-hour drive, and I'm really wondering if the mechanical pump just can't keep up at 4psi. My problem really sounds like the problem the 500EFI had before the mechanical pump was added in 2001 or 2002.

Well anyway, we're heading back to Powell tomorrow morning so I'm gonna put the hammer down and see how it runs up there again. If I still have a problem I'll probably change the mechanical pump and go to a better filter/water separator. I have a fixed gauge now on the mech. pump that shows me max pressure so I'll check it at Powell and see what it puts out again.

Again the tank vent seems to be OK & clear. If I have the problem at Powell I may try running with the gas cap off. The petcock is wide open and all the fuel lines are tight. I thought about removing the petcock all together thinking it may be a restriction but haven't done it. So we'll see what happens. :crossfing

[Dr. Dan]

:bonk: Rick ... I have not read all of this thread so I apologize if this might have been mentioned before...and I have no idea how you would determine this... but could there be an obstruction or peice of something... restricting fuel out of your tank...and it gets sucked into the line feed only upon just the right circumstances? I don't know how or why there would be anything in there... but as you describe the symptoms sporatic occurance...its seems like if its not ignition related ... well?

The injector test mentioned above seems like a shot.... man this sucks... I feel for ya... :wink:

Good Luck

Doc :smash:

[RickSE]

Well we're back. I did some serious running above 5,000 RPM's and not one hickup. The boat ran great and was on rails all weekend. :wink:

Now I just need to fix my exploded speedo tube so I can get my speedometer back.

[Mr X]

Well we're back. I did some serious running above 5,000 RPM's and not one hickup. The boat ran great and was on rails all weekend. :wink:
Now I just need to fix my exploded speedo tube so I can get my speedometer back.
Rick, glad you got it fixed. I still remember the very first day I put your boat in the water and ran it.......
It is my favorite SE made! :wink: