Stock 7.4l carb mercruiser gen5
The port engine will start, idle and run fine in gear at various RPM's for 5 minutes, 15 minutes, whatever, runs normal then suddenly dies when being returned to idle and usually will not restart and run correctly. End up idling in on one engine twice this past weekend.
Back at the marina from cold the same port engine will start and die, won't idle or hold rpm if accelerated, never gets started correctly. But then suddenly it starts and run correctly. Very intermittent, thinking electrical and not knowing where to start. Plugs look good and is getting fuel.
Suggestions ?
Thanks, ed

Put a timing light on any plug wire. When engine won't run, crank. If you have timing light flash, rebuild the carb. If light is dead, ignition is intermittant.

check the cannon plug for corrosion ,i have seen this cause all kind of problems.

It will always fire, just won't keep running sometimes. Carb was rebuilt in June.

also could be the coil,ignition module.

Under $10 !
All parts stores have them:

You can find some of these under $30 or in your buddies garage free.

Have them.

I have a spare coil so since it's a quick swap i'll try that first.

What is your serial number?