OMC Chevy 5.7 just cuts out.

[Teacher48]

So my son bought a 1992 20 ft open bow sunbird this past summer. 5.7 , very good consistent compression, clean looking engine. It had some running issues so I rebuilt carb, changed one way fuel valve near tank, new plugs and runs fine now. The issue he is having is that it will suddenly just stop when up on plane for maybe 1 second or sometimes 2. It happens after maybe 20 or 30 minutes of riding, engines dies then starts again on it own a split second later. Or it will die altogether but then restarts easy and good again for 10 to 60 min or even longer then it does it again. Has always restarted easy and never has never happened at very low speeds. On some outings it never happens. In the spring we are planning on changing the points, condenser, cap and wires, but I don’t thinks that’s the issue. It shifts very easy ( cone clutch I think) smooth and without issue. Anybody have anything like this?

 

[gm280]

The first thing you have to do is try to figure out if it is electrical or fuel issue. Sounds simple but that will lead you quicker to the problem. If you can monitor the spark and see if you still have spark when it dies, that would at least help direct you to electrical or fuel issue. Even taking a Tiny Tach and wrap the pick up lead/wire on to a spark plug wire will show that issue easily. If the Tiny Tach stops displaying the RPMs, you found your problem. Well at least you will know it is electrical. Then back up and go through the entire spark system 'til you locate a suspect part or parts. Heck, even a pulse triggered timing light clipped to a plug wire would do the same thing. Could easily be the capacitor in the spark circuit going bad intermittently. JMHO

 

[Teacher48]

Thanks for your reply. Yea I definitely thinks it’s an electrical issue. Not familiar with a Tiny Tach but will look it up. Thinking it may be involved with the EAS modular but will need to carefully check out all the wires.

 

[alldodge]

If the tachometer shorts out it kills power to the coil.

Could be key switch or kill switch or just a bad connection

 

[QBhoy]

Sounds electrical for sure. I’d check all the usual battery terminals and the main earths. Also the lanyard kill switch system too.

 

[gm280]

Thanks for your reply. Yea I definitely thinks it’s an electrical issue. Not familiar with a Tiny Tach but will look it up. Thinking it may be involved with the EAS modular but will need to carefully check out all the wires.

Search for the "Tiny Tach" and you will see a self contained digital tachometer that uses a wire wrapped around any spark plug lead to trigger it to display RPMS. And since there no direct connections to the engine, it doesn't effect what is going on. But it will stop displaying RPMs if there is no spark signal. That is why I stated using such a device. It would prove you have spark or no spark when the cut off happens...

 

[Lou C]

What ignition system does this engine have? The older models like mine had a simple points & condenser distributor with centrifugal advance. I looked up the engine on a parts website and it looks like you have the Prestolite BID system, the modules for these are NLA, but you can either replace it with a Petronix or replace the whole thing with a Delco EST distributor if loss of ignition turns out to be the problem.

 

[Teacher48]

Thanks for your responses. It does have points and condenser which we are planning on replacing. But Im hoping the issue is just a loose wire somewhere in the ignition system. Like I said it just doesn’t happen if below say 6 miles per hour in calm water. We did have issues with the throttle control getting it in proper position so engine will turn over. Pain in the butt but I think just moving wires around and hoping to create the issue. Then carefully inspection after that. Any idea how I will know exactly what distributer I have. Certainly could be the Prestolite but not sure.

 

[Lou C]

Post up a pic

 

[Teacher48]

Boat is put away for winter, will need to wait until spring. Thanks for your interest.

 

[Lou C]

Here's what a Prestolite points distributor looks like with the cap off. This one's for a 4.3 V6...

 

[Teacher48]

That’s what I remember it looks likes but then again, what’s my other possibility? I think this motor had two different distributors used in them. Seems like all points and condensers look like that. Thanks For your effort.

 

[Lou C]

Sure thing, well the only other thing it could have is the Prestolite BID (electronic) which has a module there instead of the points & condenser. If its really a '92 then I don't think it came with a points distributor unless someone changed that along the way...because maybe the module failed and they couldn't get a replacement. That BID system was used on OMCs and Volvos for few years and was replaced by the Delco EST system, which is still available new if you wanted to switch to that.

 

[Teacher48]

It definitely could be 1991 not 92. Definitely has points. I cleaned them a bit last summer but needs replacement. Don’t want to change over to electronic.

 

[SleeplessDream]

check your electrical connection to your shifter. There is an interupt switch upon changing forward/reverse. On the older model it was module with Manual relay. The newer update is electronic module solid state. Worth a look maybe defective. The purpose of this switch is to interupt your ignition in order to shift. That micros switch sometimes fail.

 

[Teacher48]

Thank you for your input. The shifter has given us some issues at times with getting it to turn over. Come spring thats the first thing going I’m to take a look at. Hopefully I’ll be able to replace or fix that micro switch. Given how suddenly the engine dies and then suddenly starts again the micro switch issue seems very responsible.