Engine quits after short time while under way.

[82renken]

I have a 2.5 liter, 4 cylinder OMC engine and OMC outdrive in my 1982 Renken bow rider. The engine will start up and idle fine but after about 1 minute after being under way (3/4 to wide open throttle) the engine RPM's begin to drop off and the engine eventually stops completely and will not re-start until it completely cools (about an hour later).

The engine acts like it is starved for fuel. I have replaced both fuel filters on the system. I cannot replicate this issue at home with muffs on the outdrive. A mechanic friend of mine suggested that the fuel system is getting vapor locked. Is this possible while at WOT? Could this be an engine over heating issue? The water temperature of the river that I've been getting stranded on is around 82 degrees and the engine is hot when this problem happens. Could the colder hose water/muffs be preventing (and be preventing me from causing the same situation at home) a fuel system vapor lock condition due to the cooler hose water?

Thanks in advance for help. Although rowing a 18' boat back to the marina is a great upper body work out it's getting kinda old.

 

[Howard Sterndrive]

Re: Engine quits after short time while under way.

vapour lock doesn't just start on a 30 year old boat... it is a result of poor design of fuel line routing near very hot components

instead of waiting an hour- pour some gas down the carb throat and see if it restarts
sounds like you are running out of gas...either the fuel pump is weak, or the fuel isn't coming from the tank properly - i.e. blocked anti-siphon valve or lines.
Or, your carb float might be stuck, or carb bowl full of crud

Could this be an engine over heating issue?

what does the gauge say?

 

[82renken]

Re: Engine quits after short time while under way.

The gas tank is full of fresh gas. I bought the boat last fall from a person who had let the boat sit outside uncovered for a few years in northwest Ohio. The tank was empty when I bought the boat and there was some condensation in it. I put a few gallons of gas in the tank, raised the front of the boat up, and pumped out the tank as far back as I could using a hand pump. I did this several times.

I think that the carb is fine because I can run it for an extended period of time using a hose and muffs at all RPM's.

 

[lifttech2]

Re: Engine quits after short time while under way.

My gess is there is a air leak in the fuel system. during the period your engine is slowing down and before it stalls can you pump the fuel line blub and see if that gives you more rpm and corrects the motor stalling. i had the same thing and was able to track my problem to the fuel tank connection and was able to put a tie rap around the two fittings on the tank and this held the fittings together and got me home. that is if you have a line with a blub in it. other wise you might still have a air leak. happy boating!

 

[Howard Sterndrive]

Re: Engine quits after short time while under way.

I think that the carb is fine because I can run it for an extended period of time using a hose and muffs at all RPM's.

yeah, a lot of people think because the engine revs up fine in neutral, it has power....not a valid test.
It takes about 8HP to spin the drive and propeller in the driveway.... all you verified is that your engine makes an honest 8 horsepower

an engine can run at 4000 rpm with no load on it on 1 gallon of gasoline per hour....enough to make 8 hp
under load your engine uses about 12 gallons per hour to make 120hp

the carb needs to flow 12 times as much fuel under full load

the power comes from the gas - in the driveway, the carb is teaspooning it in... on the lake, the carb has to spray it in like a hose....

 

[paultjohnson]

Re: Engine quits after short time while under way.

yeah, a lot of people think because the engine revs up fine in neutral, it has power....not a valid test.
It takes about 8HP to spin the drive and propeller in the driveway.... all you verified is that your engine makes an honest 8 horsepower

an engine can run at 4000 rpm with no load on it on 1 gallon of gasoline per hour....enough to make 8 hp
under load your engine uses about 12 gallons per hour to make 120hp

the carb needs to flow 12 times as much fuel under full load

the power comes from the gas - in the driveway, the carb is teaspooning it in... on the lake, the carb has to spray it in like a hose....

Interesting HS... I love tid bits of info like this......................i have wondered about this before [how muck more fuel it takes under load ]

 

[airdvr1227]

Re: Engine quits after short time while under way.

Agreed. Sounds like you have air getting into the fuel line from somewhere. Put a clear plastic line in somewhere close to the carb and see if there are bubbles with the fuel flow.

 

[a70eliminator]

Re: Engine quits after short time while under way.

Pull the dip tube, it's probably a clogged sock filter, also check tank fittings and anti siphon valve.