Logo

95 mercruiser 7.4L stalls after warm and doesnt want to fire until igniton switch is turning off

Josh P

New member
Serial number OF413344 I have replaced numerous parts. Has new batteries, igniton switch, starter, stater solenoid, plugs, wires, cap, rotor, ign coil, and distributor sensor. Made sure sure wiring harness pins are opened for good contact and added some dielectric grease. Also has a new carb and mech fuel pump and seems to be getting fuel. It's kinda looking like it could be an ignition control module or possibly bad gas. But didn't want to spend $400 for ICM and that not fix it. Lookin for help here as I've already pulled all the hair our of my already hairless head.
 
do you have a spark tester??? Or a timing light???

I think checking for the presence of spark would be a good thing to do.
 
do you have a spark tester??? Or a timing light???

I think checking for the presence of spark would be a good thing to do.
I don't have spark tester but I did pull a plug wire and ground it to the block and was getting spark. I used a timing light at the end of last year and made some slight adjust to timing.
 
I don't recall checking the spark right after it stalled. I have checked it for spark more than once on different plug wires and seemed to be getting a noticeable spark. The more I thought about it the last time I had it on the water it was cutting out under acceleration. And the tach started bouncing all over. From what I'm gathering it's pointing at an ignition module which is about only ignition part i haven't replaced and from what I understand there is no way to test but with a new one. Any thoughts?
 
could be the module...may not hurt to try it with the tach disconnected...one of the failure modes a tach can have is to kill the ignition circuit.

And it would be prudent to verify the spark condition when the trouble occurs. Some components are known to "fail when hot"...
 
Is there any reason this aftermarket distributor with built on coil pack and sensors would not work for my set up? Looking to replace or bypass tb v ignition module that mercury discontinued. Again 95 merc 7.4/454 is what we're working with.

Screenshot_20230605_194423_Amazon Shopping.jpg
 
Would it work.....maybe.

There was a review that touched on my favorite topic - the certification label showing compliance to "marine testing" and that review said the manufacturer couldn't supply any documentation there...so that's a red flag to me.

The other concern is the timing advance approach used - no discussion on that anywhere - another red flag...

If you prefer the GM-HEI style, I'd suggest the davis unified ignition products - they are marine rated and the OEM will tailor the ignition advance curve if needed...the only drawback I know of is that they can get backlogged sometimes....
 
Installed a new hei distributor to try and bypass the discontinued ignition module but haven't had a chance to run it yet. Boat has always had some teeth missing on the ring gear and I think I had the timing too far advanced and furthered the issue. It's at the shop awaiting the a new flywheel or ring gear.
 
Back
Top