Help!! The boat that doesn't stay running.

[AndyPrev]

Hi there,
Having some problems with my 1978 omc 120hp inboard. I think that there is a problem with the water cooled intake or exhaust manifold because they have changed everything else. The problem starts after about 11 min of running time the motor stops it as it has begun to run real lean in the middle of the lake. Could there be a problem with the intake and the exhaust manifold could it be cracked which is causing the mixture to become to lean with not enough fuel? The carb has been checked and is running good on another vehicle. Would love to have this thing running before the season ends. We have put new fuel pump, + elec pump ahead of it and fuel is under pressure. redid all the electrical, plugs,wiring,points everything.

 

[Gary H NC]

Re: Help!! The boat that doesn't stay running.

Try running it on a portable fuel tank. That will tell you if you have a plugged pickup screen in the tank or a sticking anti-siphon valve as well as bad fuel..

 

[hullofalottatrouble]

Re: Help!! The boat that doesn't stay running.

did you test the pump pressure or the vacuum in the fuel system? could be a restriction in the line.. or a leak.. and are saying you have two fuel pumps on the same engine?

is this a marine or auto carb? you mention it runs good on another vehicle? did you adjust it to run on the boat once you switched it over?

done a compression test? vacuum gauge is handy as well for diagnosing problems as well..

 

[AndyPrev]

Re: Help!! The boat that doesn't stay running.

We took the screen right out and the fuel is there. We even sucked fuel out of a portable in case there was a crack in the fuel pick up line. But the fuel is there.


We are precharging the manual pump and there is lot's of pressure. The carb was tested on a pontiac that runs the same style of carb and it worked fine on both. The problems start after the motor is warm it begins to lose power like it is running out of fuel. The motor has been totally rebuilt by a marine mechanic but still it won't stay running.

 

[Don S]

Re: Help!! The boat that doesn't stay running.

Try the test procedure in the link below. Hook the gauge up, then take the boat for a test run and see what it does when the problem occurs.

http://forums.iboats.com/showthread.php?t=167561