Can Bad Wiring Cause Engine Stalling?

[Haody]

This may sound like a dumb question but can wiring issues cause engine to stall? The reason I ask is because my boat (1984 SeaRay Monaco 5.7L) runs like a champ for the first 15-20 minutes we take it out (every time). But after that we experience sporadic engine stalling. We could be cruising or running WOT and it would fall on it's face like someone turned off the key. Is it possible that I have one or multiple wires resting on the engine and once it's hot it's causing these issues? Could there be a a ground wire of some sort that doesn't have a good connection? Speaking of which, which component(s) have a ground wire? Sorry for all the boat newbie questions.

Things I've done:

• Carb rebuild
• new distibutor cap and rotor
• new coil
• new fuel pump and filter
• new spark plugs and wires
• oil changed
• total timing advance adjusted to 32 degrees at 3000 rpm

 

[nickdcj7]

that sounds to me like a bad coil. runs great until it gets hot and then the coil windings start to act funny when they warm up.

 

[KC_Sundancer]

You may also want to check the large wire harness plug on top of the engine.
Make sure it has not come loose or worked it's way out.
Had that issue with our Pachanga.

 

[Haody]

that sounds to me like a bad coil. runs great until it gets hot and then the coil windings start to act funny when they warm up.

Updated first post, put new coil in it as well. The coil is semi cool to the touch when the engine has been on for a long time, if that matters. it's not hot at all.

 

[Alegria]

Yes absolutely it could with our vintage of boat and engine. I had a very similar issue occurring with my port engine. Same exact symptoms. I was thinking it was fuel starvation, fuel pump, anti siphon valve, gas lines, carb... You name it.

I was down trouble shooting the issue last Friday. I noticed that my tach was off a bit. I tapped the tach and the port engine died. I re-started and tapped the gauge and it died again. I took the dash panel out started the engine and tapped on the wire harness and the engine died. I then looked closer and found that one of the bolts backed off from the stud on the gauge and was causing an intermittent connection. The purple wire on the tach feeding my voltmeter was the loose wire.

Tightened the connection, rechecked the others and no more issue.

 

[Haody]

Yes absolutely it could with our vintage of boat and engine. I had a very similar issue occurring with my port engine. Same exact symptoms. I was thinking it was fuel starvation, fuel pump, anti siphon valve, gas lines, carb... You name it.

I was down trouble shooting the issue last Friday. I noticed that my tach was off a bit. I tapped the tach and the port engine died. I re-started and tapped the gauge and it died again. I took the dash panel out started the engine and tapped on the wire harness and the engine died. I then looked closer and found that one of the bolts backed off from the stud on the gauge and was causing an intermittent connection. The purple wire on the tach feeding my voltmeter was the loose wire.

Tightened the connection, rechecked the others and no more issue.

Good to know. I'll have a look at those next. There's so many freaking wires, it's overwhelming as to where to start. hahaha (i'm really crying inside when i laugh)

 

[OldSkool]

I had a harness that went over the steering mechanism. It kept shorting the computer. Found that the wire had separated inside the plastic insulation cover. The only way we found it was to run your finger over the wire and feel the gap. Here's the kicker, since the harness ran over the steering the insulation would get warm and pull the wire ends apart as it hung down on both sides of the steering. Then when it would cool down the insulation would contract and the wires would touch again. I took month to find.

 

[JVM225]

If you are getting fuel, then it sounds like it is an ignition problem.
1984 Mercruiser?
Could be coil, distibutor, pick up inside the distributor, or the ignition control module.
I experienced similar problems with one of my old motors, and it turned out to be the Thunderbolt IV ignition control module.
Having two motors made diagnosing things a little cheaper and easier for me since I just swapped stuff from one to the other until the problem moved to the other motor, then I knew I had it.
The pick up, and the coil are the two cheapest pieces. maybe you'll get lucky. The distributer and the ignition control module are pricier.

 

[Haody]

I went over all the wiring in the engine compartment as well as the dash. One of the (big) prong for the big harness looked almost like it's burned. I scrapped some of the rubber out and reconnect it. Went ahead and reorganized the wires around so that they weren't resting on the engine block. Now, i wait until the weekend to take her out again for another round of testing.

Thanks for all the suggestion, keep them coming!

 

[Haody]

Alright alright alright. Finally figured out my problem. The ground wire of the shift module was not getting a good connection. Once I wire brush the crap out of the bracket and base of the carb, problem was instantly better. It did die mid run shortly after so I repostioned the bracket and tightened it real good and it was fine. The shift module looked like an original so I'm replacing it anyway. Just wanted to post the update, maybe someone will find it useful. It may not be their problem, but it's one thing they can check. The part for mine was omc 0982749.