Boat misses and engine dies at hihger speeds

[dolens]

Hello,

I have an 03 Donzi Classic 18. It has a 5.7 liter 300 HP V8 with only 69 hours. Recently the boat has started to "miss" for lack of a better term and even shut off when reaching higher speeds. The boat restarts fine and seems to run ok at lower speeds. Its just started the last 2 times Ive taken it out. The first 3 times I had it out it never did it. The gas gauge says it almost full. Any ideas are appreciated.

Thanks

[RedDog]

Replace the fuel / water separator

[dolens]

It was done 2 days ago. The problem remained. I only ran the boat for about 5-10 minutes afterward, but I would have thought that was enough time to tell if it was going to work.

[BUIZILLA]

fuel starvation

defective fuel pressure regulator

[dolens]

fuel starvation

defective fuel pressure regulator


Thats what Ive heard from others as well, is that It sounds like its starving for fuel. The Water/Fuel separator was clean when it was changed a few days ago, so it doesn't look like water in the tank. The fact that it starts right up might rule out the fuel pump? Could a bad Plug be the problem?

[BlownCrewCab]

A bad plug will cause a miss But not kill the engine. Is it a carburated motor? Float hight adjusment? Sticking Floats?

[fogducker III]

Not sure what carb you have? Check the inline filter if you have one and some carbs have a fine filter in the base fitting. Could also be fuel pump on the way out, depending on type...? Good luck.

PS. Also remove the check valve at tank if it is still there.....

[dolens]

I don't think it has a Carb. Its Fuel Injected.

[Cuda]

Does it backfire at all before it dies?

[dolens]

Nope, Just dies. You almost cant even tell its off sometimes, until you come to a stop

[VetteLT193]

Nope, Just dies. You almost cant even tell its off sometimes, until you come to a stop

in your first post you said it has a miss and sometimes dies. what is the miss like?

if it is a minor miss...
I'm leaning towards electrical. How does the engine look? any rust? run in salt? could be a bad connection.

if the miss is a major miss, like the engine is REALLY hesitating/bucking then it could be fuel related, or it could be electrical still but directly related to a really confused sensor more than likely.

Have you 'read' the plugs? if you pull them out, do they all look the same or is one plug a different color?

[dolens]

Its a major miss. You can feel the boat jerk when it does it. I would think if it an electrical issue, it wouldn't matter whether im going fast or slow, it would do it all the time. This only happens when I start going fast. I haven't pulled the plugs yet, their getting pulled on Thursday.

[zelatore]

When it 'misses' or dies all together, you said it seems like it just shuts off? It just stops clean, almost like you turned off the key?

How about a bad connection at the kill switch? The high RPM might be have nothing to do with the engine except that at high speed the boat is bouncing around more and causing a bad connection to show itself?

[dolens]

Yes, its stops instantly, as if I turned the key. Yea, I guess that's possible as well. The boats basically brand new and hasn't been run in saltwater, but a handful of times. The weird thing is, it just started happening out of the blue. If it was a gas issue, why didn't it happen every time I took it out, not just the last 2 times. It seemed to have come on pretty fast

[yeller]

When it starts to 'miss', if you back off the throttle and the miss goes away, then I'm in agreement with fuel starvation. I had that happen to me and found a chuck of crud in the fuel filter that was limiting fuel flow. Enough fuel for low speeds, but not enough to maintain high speeds.

[glashole]

what is the dealer saying?

has it been on a scanner yet?

[dolens]

When it starts to 'miss', if you back off the throttle and the miss goes away, then I'm in agreement with fuel starvation. I had that happen to me and found a chuck of crud in the fuel filter that was limiting fuel flow. Enough fuel for low speeds, but not enough to maintain high speeds.


Thats exactly whats happening. If it starts to miss and I back off, it runs fine. Slow speed all day long its OK. I haven't checked the fuel filter yet, the water/fuel separator filter was ok and changed

I haven't had it to a dealer. I don't live near one. I do have a marina that's going to looks at it tomorrow. Is it better to only have Donzi Dealers work on them?

[RedDog]

... Is it better to only have Donzi Dealers work on them?

Nope - A Mercruiser-is-a-Mercruiser. When necessary, I take mine to a Sea-Ray dealer

[dolens]

Nope - A Mercruiser-is-a-Mercruiser. When necessary, I take mine to a Sea-Ray dealer

Good! I don't live anywhere close to a Donzi dealer.

[VetteLT193]

Thats exactly whats happening. If it starts to miss and I back off, it runs fine. Slow speed all day long its OK. I haven't checked the fuel filter yet, the water/fuel separator filter was ok and changed

I haven't had it to a dealer. I don't live near one. I do have a marina that's going to looks at it tomorrow. Is it better to only have Donzi Dealers work on them?

I'm guessing a sensor. knock sensor, air temp, throttle position sensor, or ?

TPS would be my first check... I think Fixxall has the specs on hand of the range it should be in. it's not hard to check with a basic electrical tester.

[dolens]

Thanks for all the responses. I'm taking it into the marina tomorrow. Ill let you know what I find out

[yeller]

If you changed the water separator yourself, you have enough mechanical skill to change the fuel filter as well. Check your fuel line for any kinks and change out the filter. You could end up saving yourself a bunch of money.

[dolens]

True enough! I'm definitely mechanically inclined enough to do it. Ill have a look before I send it off tomorrow. What side of the motor is it located and where do I get the new filter? I have to go to a marine parts store, or is it something I can get from NAPA auto parts?

[DonziJon]

I would remove the fuel filter again and dump the contents into a glass jar and see what the contents look like. Possably there is some water in the fuel tank and the new filter didn't have the volume capacity to remove it all and the filter has More water in it. Water in the jar will be visable in the bottom of the jar because it never actually mixes with the fuel. It will seperate out at the bottom. If you don't see any OBVIOUS water in the jar then water in the fuel is not the problem.

Doesn't cost anything to empty the filter and put it back on and try it again. John

EDIT: Fuel filter on a 5.7 L V-8 is on the right front of the engine...looks like an oil filter. I would buy the replacement from Mercruiser if possable.

[yeller]

Sorry, I can't help you with a part # and I don't know where yours will be located, but if you follow your fuel line from the water separator, it should be between the fuel tank and separator. (Mine is strapped to the stringer just as the fuel line enters the bilge).

No reason you can't get a replacement filter from NAPA. Take your old one in and get them to match it up for size. Just make sure the new one is steel and not plastic.

[dolens]

Thats what I did 2 days ago. We emptied it into a jar at the marina and there was no water in the bottom of the jar that we could see

Thanks for the info

[DonziJon]

Thats what I did 2 days ago. We emptied it into a jar at the marina and there was no water in the bottom of the jar that we could see

Thanks for the info

Okey Dokey: My next guess would be if you have spark plug wires "crosstalking" to each other, OR to Ground. The boat doesn't seem old enough for that, but if a Leaky plug wire contacts almost any metal part of the engine, it could intermitently ground itself with the movement of the boat and cause that spark plug to NOT fire....ie Miss.

Sometimes you can SEE the sparking/arcing if you run the engine at NIGHT...ie: with a DARK engine room.

One other thing: Pull the distributor cap off (leave the wires on) and look at the terminals inside. They should be Clean....Not Crusty looking. If the terminals are Crusty, scrape them off with a knife or screwdriver, etc, and re-install the cap and run the engine again. If that fixes the problem, I would replace the cap the first chance you get. BTW: You MUST use a "Marine" Distributer cap. I think they are over $40. John

[Cuda]

True enough! I'm definitely mechanically inclined enough to do it. Ill have a look before I send it off tomorrow. What side of the motor is it located and where do I get the new filter? I have to go to a marine parts store, or is it something I can get from NAPA auto parts?
Napa has a catalogue of marine specific parts.

[smokediver]

I had the same problem with the same engine , year , etc ... It was winterized when i saved her from the cold weather ... It took about 4 tanks of fuel ran through it and all was fine ... I did change the seperator a few times ... hope you are having the same problem

[dolens]

Mine was also winterized. I think running the fuel out and trying new gas is a good idea. Im going to run it tomorrow and see whats going on. It more annoying than anything, especially since I just bought it

[MOP]

Good idea to check the tank pickup, many times debri will get stuck in hte anti siphon valve restricting flow, Also there is a screen in the tube that can plug up, 15 minute job to rule those out.

Phil

[DickB]

I had the same symptoms on my Sea Doo last year. If I just slowed down a bit it would run fine, but at open throttle it would bog down after a few seconds. I too thought it might be bad fuel, so I ran the tank empty and tried a fresh fill. No help. I also ran a tank with Sea Foam through it. I could not figure out what the problem was until I tied the ski to the dock and ran it with the seat (engine cover) off. Turned out I had a cracked exhaust manifold that would only spray a lot of water inside when the throttle was opened up. Anything less than WOT and the bilge siphon would keep up. I suspect the water was spraying into the intake, but don’t know for sure. I do know that fixing the leak solved the problem.

[Tidbart]

Here is what I would do, for about $20, replace the ignition switch. Clean all the wire connectors in the process. Intermittent contacts in the back of the switch will cause this problem. Starts and runs fine, then cuts out at higher speeds, contact could be cutting out on the back of the switch, killing the engine. Rough or bumpy ride moves wires around slightly, enough to cause a headache when these switches go south. This will not set an error code, so don't pay to analyze the issue with the Merc Scan tool until you try this first, easy and cheap repalcement.
A good mech should look here first, then move on to other areas.
Don't ask how I might know this.:mad:

Good luck. Bob

[zelatore]

Here is what I would do, for about $20, replace the ignition switch. Clean all the wire connectors in the process. Intermittent contacts in the back of the switch will cause this problem. Starts and runs fine, then cuts out at higher speeds, contact could be cutting out on the back of the switch, killing the engine. Rough or bumpy ride moves wires around slightly, enough to cause a headache when these switches go south. This will not set an error code, so don't pay to analyze the issue with the Merc Scan tool until you try this first, easy and cheap repalcement.
A good mech should look here first, then move on to other areas.
Don't ask how I might know this.:mad:

Good luck. Bob

That's certainly cheap insurance and a good first step.

I was thinking electrical; in the ignition system as well, until he said it would die, but come back strong if he backed off the throttle. That makes me think fuel. If it was the ignition or kill switch I wouldn't expect backing the throttle off a little to bring it back to life.

[dolens]

Here's what I know so far. The marina has done a full tuneup and replaced all filters. They have hooked it up to a machine and the machine didn't find anything. They have ruled out a fuel issue and believe it might be electrical. I am going to mention to them about the ignition switch. They also believe it might be a coil. The computer didn't find anything but they said the coil could produce that same problem

[yeller]

Time for an update. :yes:

[dolens]

Time for an update. :yes:


Funny you said that. I just got the boat back today. After a full tuneup, spark plug wires replaced, all filters changed, and almost having the coil replaced, the mechanic figured out that it was a switch, between the shift rods, that was jiggling around whenever there was vibration. The mechanic found this out by calling Mercruiser. I guess Mercruiser knew what was wrong the instant the mechanic described it. Must be a common issue with these motors? Basically this switch is there to help the boat switch back and forth between gears. It can be bypassed, but than its pretty difficult to get the boat in and out of gear. I guess there's a new ECM you can buy that will also bypass this switch while its in gear, but that's over a grand. Thats all I know. Its going to be a test of time to see how this switch acts now. They basically moved the switch a little to try and reduce some of the vibration while under way.

[joseph m. hahnl]

Funny you said that. I just got the boat back today. After a full tuneup, spark plug wires replaced, all filters changed, and almost having the coil replaced, the mechanic figured out that it was a switch, between the shift rods, that was jiggling around whenever there was vibration. The mechanic found this out by calling Mercruiser. I guess Mercruiser knew what was wrong the instant the mechanic described it. Must be a common issue with these motors? Basically this switch is there to help the boat switch back and forth between gears. It can be bypassed, but than its pretty difficult to get the boat in and out of gear. I guess there's a new ECM you can buy that will also bypass this switch while its in gear, but that's over a grand. Thats all I know. Its going to be a test of time to see how this switch acts now. They basically moved the switch a little to try and reduce some of the vibration while under way.


Ah yes::yes: "Shiftus interuptus". He was the Greek god of the Alpha's:eek:

[VetteLT193]

Ah yes::yes: "Shiftus interuptus". He was the Greek god of the Alpha's:eek:


HAHAHAHAHAHA

too funny.

[gold-n-rod]

Ah yes::yes: "Shiftus interuptus". He was the Greek god of the Alpha's:eek:

And brother to "Coitus Interuptus." Major pain.

[dolens]

Has anyone else experienced this issue?

[VetteLT193]

Has anyone else experienced this issue?

Possibly, mine was disconnected when I bought the boat and I haven't re-connected it.

I have a carb though, and have my idle set as low as the engine can handle.

[donzi182003]

Dolens,

I own your same boat with the same engine and I had the issue. It is a neutral position switch. You would feel the boat surge but it never shut off. I however had the fault code show up when it was checked. It had the alarm go off because the computer thought i was running 4,000 rpms in neutral.

[mrfixxall]

Has anyone else experienced this issue?


YEP! ended up being the distribitor pick up coil..

I would get a refund for the tuneup for misdiagnoses..