5.7L OMC Cobra stalls without warning while under way

[Skyking 310]

I have a frustrating problem and need some advice.

Our 1987 Bayliner Capri has a 5.7L Chevrolet motor and Cobra outdrive. We can be going along pulling tubes or skiers and without warning, the motor will cough a time or two and then stop. I can shift to neutral and start it right back up without any problem and an hour or two later, it will do the same thing. We can cruise around all day if we stay below about 3,000 RPM's and it never happens, but if we get above 3,000 and start using it to tow, within an hour or two it will start playing games. The coil, points, plugs and distributor are new, and I've changed the fuel filter. Can anyone offer any suggestions or advice?

 

[Don S]

Re: 5.7L OMC Cobra stalls without warning while under way

Could be nothing more than a fuel vent being partially plugged or the fuel pickup in the tank being partially plugged. At 3000 rpm or less you are using less fuel, and fuel delivery can keep up. Above 3000, and you start using more fuel and it can't keep up.
Hook up a vacuum gauge setup on your fuel tank as in the link below, and see if you start getting high vacuum about the time the engine dies.

http://forums.iboats.com/showthread.php?t=283269

 

[dannieboiz]

Re: 5.7L OMC Cobra stalls without warning while under way

also if you have a fuel/water separator see if that's clogged. Last year, when I was 10 miles out the ocean my boat did the same thing turns out my fuel/water separator was full. Emptied it out got to shore got a new one and back out I went.

 

[Skyking 310]

Re: 5.7L OMC Cobra stalls without warning while under way

As always, Don S., thank you.

 

[Skyking 310]

Re: 5.7L OMC Cobra stalls without warning while under way

Thanks for the ideal about the fuel/water separator. I bought a new one this spring to change it, but (duh) I forgot about it.

 

[bruceb58]

Re: 5.7L OMC Cobra stalls without warning while under way

And if you do have a ton of water in there, just don't slap another on there without investigating what is in your tank.

 

[HCMQA]

Re: 5.7L OMC Cobra stalls without warning while under way

My 4.3 with Cobra behaved the exact same way. It was almost random.
Turned out to be the carb needed rebuilt.
Once you get above 3k RPM the carb needs everything working right to keep up with demand. I found small flakes blocking one of my main jets and part of the accelerator pump was clogged.
Now it runs like a scalded cat.

 

[Skyking 310]

Re: 5.7L OMC Cobra stalls without warning while under way

Great suggestion. Thank you. It's been a dozen years since I've done anything with my carb. Winter's coming so it will be a great time for me to get into it.