1992 omc 5.0 302 stalling under load

[Chuckyd973]

I own a 1988 21' bay liner trophy. It originally had and omc 3.0 with cobra outdrive. The motor blew up and I swapped in a 1992 omc 5.0 ford 302 with a 5.0 cobra drive. The issue I'm having is the the motor will stall under a load. To correct this issue I had the two barrel Holley carb rebuilt. When they rebuilt the carb they found little pieces of black plastic in the carb. We assumed it to be the fuel line from the tank to the pump. I replaced it with the new grey ethanol approved fuel line. I added an additional inline fuel filter. I replace the fuel water separator filter. Once on the water the engine runs like a bear for about 10 minutes, after that it will stall at any rpm above 2000. I have removed the fuel bowl on the carb and adjusted the float and checked for any debris to only get the same issue. Sometimes it will run for 20 minutes ith no issues and other times it will act up immediately. Being that everything In the fuel system is new, I'm beginning to lean towards ignition issues. The motor has the electronic ignition with no points. The old 3.0 had points and I feel like the engine is having the same symptoms of worn points. But there are no points here. Any help would be appriciated. Thanks

Chuck

 

[Howard Sterndrive]

Re: 1992 omc 5.0 302 stalling under load

anti siphon valve is where I would start.... that black stuff may have originated in the tank, and if so, definitely going to be chunks in the anti siphon valve at the tank connection.

what does the additional inline fuel filter look like? If you already have a separator filter, I would get rid of that. Those aftermarket spin on separator type are all you need.

There was a recent thread where Don was posting up info about the OMC factory engine mounted fuel filter housings having paint coming off the inside of the base.

 

[ccsears1981]

Re: 1992 omc 5.0 302 stalling under load

By running two filters inline I would lean toward that causing the fuel pressure to the carb to be lower. That might be the issue, without the proper fuel pressure not enough fuel is getting to the engine. Are you running it easier when it runs for 20 min compared to possible running it harder when it goes immediately?

 

[Chuckyd973]

Re: 1992 omc 5.0 302 stalling under load

When I replaced the fuel line from the tank to the separator I inspected it and it was definately breaking down internally. I pulled the sender and shined a light into the tank. It was immaculate inside. I also checked the vent lines for blockages and found none. When I get the boat cruising I keep it around 3k rpms. Never really push it hard, It was way too much work to rebuild the mechanics on this boat to go through it all again. The motor will go to 4200- 4400 rpms if I go full throttle, but never really maxed her out long enough to find out. I'm going to try eliminating one of the in line filters and see if that helps. Could also be fuel pump is on its way out. Is this also considered vapor lock?

Chuck

 

[ccsears1981]

Re: 1992 omc 5.0 302 stalling under load

Could be a fuel pump, i would test the fuel pressure should be around 6 or 7 PSI at idle for that engine if its the manual fuel pump. Vapor lock is a posibilty, usualy when they vapor lock it will not start back up until the pressure is relieved but if you have a leaking gasket then it could be possible. When it acts up again try taking the fuel cap off and see if it eliminates the problem if so then something has your gas tank vent clogged off.

 

[Chuckyd973]

Re: 1992 omc 5.0 302 stalling under load

Ok removed secondary fuel filter no change, replaced anti siphon fitting no change. Adjusted float in carb and mixture no change. The choke is staying open. I ran it with dog house opn and arrester off no change. I swapped the ignition coil with a spare I had and no change. I sprayed carb leaner all around carb and intake with no fluctuations in rpms. I guess fuel pump and timing? All I have left?

Chuck

 

[Chuckyd973]

Re: 1992 omc 5.0 302 stalling under load

Ok guys opened carb again and removed needle a seat to find it completely clogged . I cleaned it out put it all back together. Runs great now on the water as we speak.

Chuck