engine stops at high rpm

[jdeblanc]

i recently acquried a 1979 cobalt with an 800 omc stern drive. i had problems all the way. i put new starter, coil, plugs, and points in just to get the boat to start. i had to ship the upper away to get the housing replaced. i put the boat in for the third attempt today and joyously got to run the boat around the lake finnaly. everything seemed to be dandy until i decided to open her up a bit. as soon as i did open her up, she stuttered and stalled. it didn't want to start back up. i jiggled the supply wires to the distributer and it started after several attempts. it kept stalling, even at low rpms for a while, but after 5 min or so, it seemed to run fine. i took it easy till i got near the boat launch and opened it up again and had the same results. where should i start?

 

[ziggy]

Re: engine stops at high rpm

guess i'd start with some compression numbers. see if ya got something to work with. then i'd move on to a minor tuneup. points, cap, rotor, condenser, plugs, plug wires, fuel filter(s). then i'd set dwell, then timeing. then carb. adj. if nessesary. set to oem specs for your rig.....

if yer jigglin wires to get it to work. ya might go thru all wire connections. clean them up shiney. grounds too.....

yer gonna need a service manual book too. don't know which one though. maybe someone else knows.....

 

[imported_TheMan]

Re: engine stops at high rpm

Personally, in a boat that old, I would replace all the wires possible.. Corrosion of the terminals, nicks in the wires, etc could all be problems.

Have you timed the engine? And just to make sure, you have the firing order correct, right? The previous owner of my boat had the firing order hooked up wrong and was wondering why he didn't have any power although the engine ran "okay" when started...

 

[Don S]

Re: engine stops at high rpm

What engine ya got???? 4? 6? 8 Cylinders?????

 

[jdeblanc]

Re: engine stops at high rpm

it's an 8cyl engine. i have already changed the points, coil and plugs. i didnt look at the actual rpms but the boat ran great at about 30 mph. the problem occurs when i try to go faster. it completey stalls out and is hard to start. it runs like crap for a few min. then mysterioulsy runs fine again until i get above 30mph and starts all over agian. it could be just a fluke about what speed its ocurring. that seemed to be the pattern i noticed in the 40 min i was on the water.

 

[Haut Medoc]

Re: engine stops at high rpm

Sounds like a fuel delivery issue.....
I would check the fuel system from the tank pickup to the carb...
& the tank vent as well.......​

 

[Don S]

Re: engine stops at high rpm

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

 

[jdeblanc]

Re: engine stops at high rpm

Thanks for all your advice. the fuel delivery seems the most logical. ill start there and let yall know what i come up with.

 

[mille73]

Re: engine stops at high rpm

I had the same symptoms with my port engine Don S. was correct look at the fuel delivery. In my case it was the fuel pickup line at the port tank. Ran fine at the dock & up to about 2300 RPM then would bog down. Switched fuel divertor valve to run from both tanks (different pickup tube) runs fine now.