im lost, been fighting this too long, need some help

[tiger lily]

i have been fighting this problem since last year, heres the problem, when above 3k rpms i seem to be running out of gas, it falls right on its face and stalls, then takes aa few cranks to get started again, but it will start, some people have told me the float bowl might be running out of gas, ive replaced the entire ignition, fuel filter, checked the lines, replaced a couple old fuel lines, fuel pump is working good, compression tested the engine, the only thing left is the carb, now im pretty good at working on engines, however i dont do carbs, my dad isnt very great with carbs either, so im thinking about taking it in to have it rebuilt, but i dont trust many shops(thats why i always do my own work) but is there anything i should check before i take it in? the engine is a 351 SBF with a holley 4 barrel.

[MOP]

Have you pulled the tank pickup, having debris in the anti syphon valve or pickup may be causing a fuel restiction.

Phil

[Carl C]

What Mop said and did you check fuel pump volume and pressure at the carb? It's very easy to remove the float bowls and check the float level and the needle and seats.

[tiger lily]

im almost positive its nothing in the lines, i can make it do it everytime on command with how hard i hit the throttle or by easing it to it, i have a time limit before it stalls and runs out of gas.

[mphatc]

Matt,

If you run full throttle IMMEDIATLY after start does it run out of fuel as soon as it hits 3000 rpm, or will it run up higher for a short period and then starve?

What is your fuel filter?
How large?
Is your fuel tank original?
Is this carb the same one that hs been on the boat for a while?

Mario

[Moody Blu']

sounds just like my problem. the stock pickup has a screen and all the particles collect around the pick up and then fall down when finally off. if its not a stock pick up then it might not have a screen. i put a larger pick up in my tank to help with the clogging and now i just blow it out when it gets stuck once my tank is half full

also, i made a very stupid mistake once when i first installed my fuel pump and ran it into the intake (per this guys instructionswho sold it to me)and it was not allowing my fuel pump to function properly i doubt thats your problem.

[DonziDave]

I chased the exact same problem last year. Drove me nuts....!!!!! Turned out to be the lining in my 20 year old Aeroquip fuel line was slouffing off and clogging the fuel filter. I dumped the gas out of my filter into a glass bowl and saw little flakes. I poured the gas onto a screen and let the flakes dry. When I picked them up they were pieces of rubber. Replaced the line and no problems since.

A simple test before you start tearing into mechanicals.

Trust me, I know how frustrating this can be..... :smash:

Dave

[tiger lily]

the fuel filter is a canister type, ive drained it many times and replaced the filter inside it already about 10 times, i had no water or debris in there, i guess ill stuff my narrow ass under that deck and try to get to the tank, yes it is the original tank.

[tiger lily]

Matt,
If you run full throttle IMMEDIATLY after start does it run out of fuel as soon as it hits 3000 rpm, or will it run up higher for a short period and then starve?
What is your fuel filter?
How large?
Is your fuel tank original?
Is this carb the same one that hs been on the boat for a while?
Mario

it will tach out and run real smooth right till it stalls, if i hit it hard, it will only run for about 15 seconds before stalling, when i run about 3k say set the throttle at 3400, it will run for a few minutes then stall. seems like when the back to barrels should open, they dont?? its a vacum secondary carb

[Moody Blu']

um the fuel pick up is really not accesible unless you have a access hole cut out right where the pick up is. luckily my boat came with it.
heres my old original interior if you look real close in the middle between the seats you can see the access hole. i could get you better pics if you would like.
what year was yours?

i wonder if the pickup location was ever changed?

it does sound like it could be carb related also though.

best bet to eliminate the carb quick is either borrow or clean your carb and buy a gasket kit.

http://www.donzi.net/forums/attachment.php?attachmentid=8717&d=1104988139

[Cuda]

It took me a year to chase down the same sort of problem on my Formula. It would run fine, rev to 5200 perfectly, in the driveway. When I tried to get on a plane, the starboard engine would die. Turned out it was a weak fuel pump.

[Woodsy]

Have you replaced the key switch? You would be surprised what gremlins that little device can cause...

Woodsy

[Pismo]

Try alternate fuel supply, unhook the stock fuel line at the water serparator, and plug it, attach a 3 ft piece there and stick it in a 5 gallon can. You will ABSOLUTELY know if it is the fuel tank, fuel line, fuel vent, pickup, etc in less than 5 mins. If you still have the problem then it is upstream.

[joey donzi]

Had the exact same problem fixed by what mop said...

[Formula Jr]

even if you find some obstruction to the fuel screen, your description points to mid range jets in the carb being obstructed since it happens at exactly the same rpm. Carbs are not that difficult to take a part and rebuild.

[tiger lily]

ive got a fuel presure gauge hooked up to it right now, but my dumb ass forgot to turn the gas switch back on before i started it, ran it out of gas, then flooded it trying to start it back up, will return later with gauge results. boat ran fine almost all last season, then this problem started pretty much out of nowhere.

[Moody Blu']

what year is your donzi

[tiger lily]

what year is your donzi
it is a 78

[mrfixxall]

ive got a fuel presure gauge hooked up to it right now, but my dumb ass forgot to turn the gas switch back on before i started it, ran it out of gas, then flooded it trying to start it back up, will return later with gauge results. boat ran fine almost all last season, then this problem started pretty much out of nowhere.

tiger take the fuel line off and the gas cap and blow air through the fuel line to see if its pluged...

[Marlin275]

I had this same exact problem when I bought my Donzi 5 years ago.
Right at 3000 RPMS the nose sticks up and the tank debris clogs the pick up.
when the boat sits flat you could rev it all you want.
Put in new fuel tank, solved the problem.

Pismos idea will help test for bad tank.


Try alternate fuel supply, unhook the stock fuel line at the water serparator, and plug it, attach a 3 ft piece there and stick it in a 5 gallon can. You will ABSOLUTELY know if it is the fuel tank, fuel line, fuel vent, pickup, etc in less than 5 mins. If you still have the problem then it is upstream.

[joseph m. hahnl]

holly carbs are the easiest to work on. They also use the crappy powervalve which can cause exactly what your talking about. the can blow out from a backfire thru the carb. Most holly problems are power valve associated.
Also : you can check a holly really easy for float level and gas they have a sight screw on the side of the float bowl. as soon as it dies take out the screw and you will be able to see if the carb still has gas. I would also suspect the o ring from the primary fuel tube to the secondary float bowl "its the aluimnum tube on the carborator"
unless you have a dble pumper .if that tube is plugged the secondary float bowl will never get fuel.


joe

[Ed Donnelly]

Holly has a simple fix for the power valve problem....Ed

[Cuda]

holly carbs are the easiest to work on. They also use the crappy powervalve which can cause exactly what your talking about. the can blow out from a backfire thru the carb. Most holly problems are power valve associated.
Also : you can check a holly really easy for float level and gas they have a sight screw on the side of the float bowl. as soon as it dies take out the screw and you will be able to see if the carb still has gas. I would also suspect the o ring from the primary fuel tube to the secondary float bowl "its the aluimnum tube on the carborator"
unless you have a dble pumper .if that tube is plugged the secondary float bowl will never get fuel.
joe
They have a kit that fixes the blown power valve trouble. Shouldn't a blown power valve make it run rich all the time? And yes, I agree that a Holley is by far the easiest carb to work on.

[tiger lily]

well i ran it on the hose with the gauge, i got about 4 1/2- 5 psi of presure at idle, tomorrow im going to put it in the water, have someone watch the gauge and tell me if it falls off right before it stalls, that should(i hope) tell me which end the problem is on.. i read in my book about the site screw on the carb however, i must have a wierd carb or something because it does not have one, the book shows right where it should be, and its not there, ill snap some pics tomorrow of it and post them, i really appreciate all of your guys help and input, this is driving my dad and i nuts, we had a similair tank problem with a 88 baja, but that turned out to be plastic in the tank and it was a constant problem like this one, that one was random, this one is very predictable when its going to stall.

[DonziJon]

OK: Here I am.. sticking my neck out YET AGAIN: I'm a simple guy who likes "Simple" solutions...IF they are available. Let's put some "DryGas" or "Heet" in the gas tank and see if maybe water might be the problem. Cost's about 8 bucks for a 40 gallon tank. It's Simple..and you should do this Every Year ANYHOW.

Water doesn't mix with gasoline. It just floats around in the bottom of the tank...FOREVER..IF you don't remove it. OH wait: It "sometimes" likes to get sucked up into your fuel intake pipe and screw things up.

SO: These two products are ALCOHOL. They mix with gasoline AND..they mix with water. SO: Put that stuff in your tank and the water..IF ANY, will tempororarily mix with the gas and "Run" through the engine during normal operation. Try it. If it doesn't improve the situation..you've only lost 8 bucks. AND: It's easy. :smash: John

[tiger lily]

john, when this problem last year started, that was our first thought, i filled up at put in bay island to get home from there, well that was the first night this happened, we had heard other people say they got bad gas there that weekend too, it was xmas in july, big weekend there, well ive ran SOOO much of that through the boat that if there was any water in there, its for sure gone, and we always put that in our tanks before winter storage also, i siphoned damn near the entire tank last summer, put all the gas in 6 gallon cans, tied them upside down from a tree(knowing that water is heavier than gas it should bring the watery gas out first) and drained them, and didnt get what looked like any water out, needles to say, i did not waste that gas, we ran it in our lawn mower for the year and i stuck some of it my ranger, neither those had and misses so thats why im thinking something diffrent, there also was no varnish in the gas that was sucked out either, nor in the filter.

[Formula Jr]

Tiger,

I can certainly understand your frustration. My borther had a jet boat once that would sputter and stall right when it hit about 3K. Even took the carb apart twice and it was still there.
Then took the carb apart a third time and found the circuit that was gummed up. Ran like a dream after that. There are differing opinions on the best way to winterize. Some say drain the tank completely, some say fill the tank and add stabilizer, but be sure to run the floats dry. I think a steel tank should be stored full with stabilizer. You said you drained yours. This lets the walls form surface rust. You have 4.5 PSI and that is good pressure. You could also do a flow rate test. I don't recommend this unless you have some one holding a fire extinguisher on you during the test and you know you have no cross fire. At idle I think its a quart a minute. But a service guide will give the real spec. The big clue that its a carb problem, is that it happens at a certain RPM and feels like fuel starvation, or in other words too lean a mix for the manifold vacuum. If your bowls were not filling at the proper rate, you would have at least some time at WOT before it ran lean then crapped out. But you never get there according to your description. Its fine at idle and then it dies at 3k which is right where most carbs change circuits. And a Vee Hull is loading "if thats the proper term" right here trying to get on plane. Its also the one thing you have not looked at. If it wasn't a deep vee, you could probably "pump the throttle" through this middle zone and get to WOT. You have'nt said if you can do this. I've dealt with many boats that "sat" for a while and this is common. You just pump the throttle till you get the WOT circuit going. Then you rebuild the carb when you know its that.

Test it in a progressive manner, very slowly bump the throttle up from idle. If its exactly the same place that she burps and dies, its the carb.

[tmdog]

If I was a betting man ,I would say a weak fuel pump. Testing the boat at speed and keeping an eye on the fuel pressure gauge will tell.
Also a cracked fuel line or pin hole that causes air to be sucked in will the fuel.

[Rootsy]

this issue only occurs when the engine is under load?

[DonziJon]

john, when this problem last year started, that was our first thought, i filled up at put in bay island to get home from there, well that was the first night this happened, we had heard other people say they got bad gas there that weekend too, it was xmas in july, big weekend there, well ive ran SOOO much of that through the boat that if there was any water in there, its for sure gone, and we always put that in our tanks before winter storage also, i siphoned damn near the entire tank last summer, put all the gas in 6 gallon cans, tied them upside down from a tree(knowing that water is heavier than gas it should bring the watery gas out first) and drained them, and didnt get what looked like any water out, needles to say, i did not waste that gas, we ran it in our lawn mower for the year and i stuck some of it my ranger, neither those had and misses so thats why im thinking something diffrent, there also was no varnish in the gas that was sucked out either, nor in the filter.

OK: You say you've run bunches of "drygas" through the system including winter storage.. One of the recent questions being raized today concerns Alcohol in the fuel and older engines with fuel hoses, seals etc. that get "mushy" when Alcohol is used in the system all the time. I'm still looking for something simple. Someone DID suggest bypassing the built in fuel tank and system with a temporary fuel tank and line. Pick up a cheap plastic "outboard motor " fuel tank from West Marine to bypass everything to isolate the problem. John ;)

One last thought: I've never had a four barrel carb apart...BUT..is there a small "Porous Bronze" filter at the junction of the fuel pipe and the Carb??

Later: I just looked it up. THERE IS a small filter shown at That Location on the Rochester Quadrajet and and a couple of the Two BBL carbs in my "Clymers" exploded view carb breakdowns.

[joseph m. hahnl]

I'm going to have to agree with F JR. I would say if you have never taken the carb off and the float bowls off ,the carb is dirty. probably Fouled jets I would say on the secondary side. 3K is were the secodaries should start to open.If it runs on the idle circut, and the primary circuit with out dying out .
You can watch the trucks with the flame arrestor off and see if atomized fuel comes out of all four of them.There is a big difference between wet fuel and dirty fuel.Water with a little help from dry gas will pass the water thru the jet.
particle contamination will be for ever trapped in the bowl chamber until you physicaly remove it with compressed air.

The worst thing is rust. rust can be .0015 in dia and smaller. So small that it is impossible for the human Eye to see it. It can get thru most filters . It is a real mother to get out of the carb . It sticks to the side of the bowl as you dump out the fuel. It really likes to hang on. I had this problem in my Honda. I would dump the gas. used compressed air to blow the bowl out. I added clean fuel to the bowl and watched it. I could see the metal"rust particles" come right back off and the bowl was still dirty.


any way


joe

[tiger lily]

*update*

ran the boat on the lake tonight with a fuel presure gauge hooked up, i had my dad ride along with me, he watched the gauges, i watched the water in front of my, 2500 6psi, 3000 6psi, 3800 6psi and starting to fall very slowing, 4000 5 psi and starting to fall, within 10 seconds i was down to 2psi and it was starting to stall, pulled back the throttle and stabbed at the throttle and i was able to keep it running, all the rpms we set the throttle at and cruised to get a acurate reading, running back across the lake, which was about a mile or alittle more, we saw 6psi on the gauge the entire time, and it held there while we idle to the ramp...

now i also want to let everyone know when i winterize the boat, i put stable in the tank and the tank is competley full, we also fog the motor every year, so the next step im going to do, is take my dads tank that he has for his zodiak, which is a 5 gallon plastic outboard tank, hook it up, and repeat the same thing i did tonight, im hoping that will tell me where to go, thank you all very much for your input, this is one of the biggest PITA's ive had in awhile

matt

[MOP]

Matt I am even more sure of fuel restriction now, run it on a remote tank. Do not use a standard outboard tank they do not flow enough at high speed. I am willing to bet if you secure a 5 gallon jug well enough to run and run a good 3/8 hose to the pump it will run fine, a fuel pump will only vary pressure from RPM or restriction. I still say get the tank pickup out, check it and the anti syphon valve along with the hose from the tank to the pump!

Phil

[Moody Blu']

it still could be either a fuel tank clog or a carb

but the last hting you want to do is take apart the carb, so you rnext step is to get a separate gas tank and run the boat off of that use the pressure tester too see if its any different.

does really sound like a tank problem though, there "classic" for that

[MOP]

"T" a vacuum gauge into the fuel line coming from the tank 3-5 inches is acceptable, much higher and you have problems. That will tell you if it is on the engine or in the tank.

Phil