Mercruiser 120 runs for ONE hour then backfires and stalls - tough to restart

[kcasey2159820131]

My Mercruiser will religiously run for 1 hour then backfire and stall. Temp guage reads normal; plenty of fuel.<br /><br />Has anyone ever seen this type of problem?<br /><br />Thanks,<br />- Case

 

[Northern Eclipse]

Re: Mercruiser 120 runs for ONE hour then backfires and stalls - tough to restar

Re: Mercruiser 120 runs for ONE hour then backfires and stalls - tough to restar

Check ignition coil and condenser for voltage, there are a few post active at this time addressing how to check Coil and condenser. when it fails does it start right up or do you have to wait a bit?

 

[kcasey2159820131]

Re: Mercruiser 120 runs for ONE hour then backfires and stalls - tough to restar

Re: Mercruiser 120 runs for ONE hour then backfires and stalls - tough to restar

I have changed the ignition coil recently, but i will check voltage again. <br /><br />YES, the engine is still rough until it cools down. Another smaller outboard engine gets me in and same thing the next day - Starts FINE, runs for 1 hour FINE, then backfires and same same.<br /><br />Thanks

 

[kd6nem]

Re: Mercruiser 120 runs for ONE hour then backfires and stalls - tough to restar

Re: Mercruiser 120 runs for ONE hour then backfires and stalls - tough to restar

Is it losing spark when hot? I'm probably being really silly here but check the voltage feeding the coil to make sure it is interrupted when the points open (or sensor triggers), and bottom line it has to spark. Pull a plug wire and watch it jump is really the way to do it. Could be as simple as a bad condenser.