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Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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I have a 1988 mercruiser 4.3lx 4bbl with the thunderbolt

Customer Question

Hi, I have a 1988 mercruiser 4.3lx 4bbl with the thunderbolt ignition. Ran great last year, pulled it out this year and it runs good for 20 mins or so then falls flat on its face if you try and run her above 3k. Only happens once engine is warm. Cleaned fuel system, took to a shop which they misdiagnosed as a bad ICM. I recall a similar issue on my old OMC 5.0 and it ended up being the ignition sensor under the distributor cap. If it matters, the issue only seems to happen under load. In my driveway it ran like a charm for an hour. No issues starting up when it does this, just going above 3k it falls flat on its face. No missing or anything, just acts like engine ignition is turned off. Should I replace ignition coil and sensor under distributor cap? Want to get my money back for that 330 dollar ICM too.
Submitted: 2 years ago.
Category: Boat
Expert:  Tan replied 2 years ago.
Hello. My name is***** will be helping you. This sounds more like a fuel starvation issue. When the engine falls flat does the engine quit? If you are running along at 3000 and the engine acts like it is going to quit will it continue to run if you pull back on the throttle real quick?

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