Stalling on 744APEPWS OMC King Cobra 454

[PSteward]

Hello!


Was out today and suddenly the motor just stopped out of nowhere. I was unable to start again (tried a few times) and pulled my tender motor to try to limp back, but luckily within 15-20 the engine was able to start back up and get us back.
On the way back I observed 14.6v+ on the starter, the engine was able to throttle and idle properly and I had no issues reversing back into the dock....we were planning a trip soon and am worried about a reoccurrance.
What kind of thing would cause this, where should I look (alternator, fuel filter++)?


Thanks for any input!


--Phil

[Khaos13]

What kind of boat are we talking about Phil? If it's a GM 454 outdrive boat it's probably not a sailboat . Still, does it have electronic ignition? Sometimes the electronic ignition modules can fail with symptoms like yours. Need more info.

[PSteward]

Hey Khaos,

It's an older (1991) 27 foot cruiser with a sterndrive. It has a distributor/ignition coil, so it's a conventional setup.
The engine generally performs ok but every once in a while this random stall out will take it out for a bit. Ultimately there are two parts, one is the stall and one is the inability to restart.
The cause is likely the same but after some time goes away.

[Khaos13]

Phil,
Your 1991 distributor (HEI) has an electronic ignition module inside the distributor cap. They WILL fail at some point. You can order one on Amazon or get one at any auto parts store. They are not expensive. Ignition coils also fail. When electronic components get hot they can fail and not work again until they cool which might explain your symptoms. To me, your problem sounds electrical and I'd start by replacing these parts. Might as well put on a new distributor cap while you're at it.

BTW, if the ignition coil feels REALLY hot while running (or just after) it's probably bad.

[PSteward]

Hey Khaos,


Are you suggesting the failure is from the "COIL,IGNITION MODULE (10)" as shown here: Ignition - 454 Models?
I know the previous owner had changed the distributor, and I recall that this component is separate, the feed to the distributor comes from it (connects to the center of it). I don't know if it was ever changed out, as you said for the cost might be handy to have a spare on hand.

[rslifkin]

Originally Posted by PSteward

Hey Khaos,


Are you suggesting the failure is from the "COIL,IGNITION MODULE (10)" as shown here: Ignition - 454 Models?
I know the previous owner had changed the distributor, and I recall that this component is separate, the feed to the distributor comes from it (connects to the center of it). I don't know if it was ever changed out, as you said for the cost might be handy to have a spare on hand.

It could be the coil (#10) or the electronic ignition control module (#9) that's failed. It looks like #9 is discontinued, so finding a replacement for that may be challenging. Worst case, there are other suitable marine electronic ignition systems out there for 454s that are used by Crusader, Mercruiser, Volvo, etc. so you could convert to one that has better parts availability (this might require switching out the distributor).

First steps would be to check the connections on every ignition related component and make sure they're clean and tight.

[Khaos13]

#9 is the ICM, #10 is the coil. First off, if the PO changed the distributor you should find out what it is. Is it stock, "high performance", or something else? Assuming it's stock, from what I've recently found you can buy the control module for 20 bucks on Amazon. Plug and play. It may not have the same spark advance curve as the marine version but it WILL run. Changing it is quick and easy. You don't need a $500 part (that Evinrude discontinued) to find out if that's your issue. The same is true with the coil. Quick and easy to change. It's a common Chevy motor; no more, no less.

[Khaos13]

Hey Phil,
I was thinking about your issue today and it occurred to me that the symptoms you described could also fit a blocked fuel tank vent. Engine runs until it can't suck any more fuel, stalls, restarts after the pressure equalizes. I've seen those cheap pot metal vents corrode so bad they're completely blocked. Check it out.

[PSteward]

Originally Posted by Khaos13

Phil,
Your 1991 distributor (HEI) has an electronic ignition module inside the distributor cap. They WILL fail at some point. You can order one on Amazon or get one at any auto parts store. They are not expensive. Ignition coils also fail. When electronic components get hot they can fail and not work again until they cool which might explain your symptoms. To me, your problem sounds electrical and I'd start by replacing these parts. Might as well put on a new distributor cap while you're at it.

BTW, if the ignition coil feels REALLY hot while running (or just after) it's probably bad.

Hey Khaos,


Tried the boat again today and it died at the same spot as last time....
I checked the voltage output from the top of the ignition coil and it was 8-11v which doesn't seem right. The model is a Diamond E-035 Oil Filled Coil.
It didn't seem that hot though, but I forgot to try the gas cap trick - after 15 min the engine started up again and was going.