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Old 07-30-2020, 05:01 PM   #1
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Default Engine stalling in idle or low rpm (solved)

Now I know how a blown manifold gasket sounds like 🧐

I know there could be a 100 reasons why your boat is stalling in low gear but after checking the fuel pump, fuel lines and filters, spark plugs, distributor cap, rotor, engine timing, throttle cables alignment and rebuilding the carburetor the tiny little fumes on top of the engine gave it away. I wasn't sure if it was just some oil/dirt residues fuming but when I sprayed some water on it I saw tiny air bubbles coming straight out of the gasket. Funny part is, this gasket is only 2 years old. Hope this helps someone out there 🤓
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Old 07-30-2020, 05:08 PM   #2
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If anyone has some ideas why this manifold gasket would get blown after only 2 years please share. I suspect reach fuel - the spark plugs were black (replaced last season). I've rebuilt the carburetor, adjusted the air/fuel mixture needle and installed new spark plugs and distributor cap/rotor. Engine temp was always good. I'm also switching to high octane 94, no methane gasoline from now on.
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Old 07-30-2020, 06:21 PM   #3
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Not sure why an exhaust leak would cause the engine to stall but the failed gasket may have caused a leak all the way to one of those intake ports and that will cause issues.
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Old 07-30-2020, 09:03 PM   #4
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Do you have a machinist ruler to check flatness on mating surfaces?
Black plugs may have been oil vice gas.
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Old 07-30-2020, 11:50 PM   #5
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Both, the engine block and manifold don't have straight surfaces, especially around the exhaust openings. I'll have to take it to a machine shop in the winter.
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Old 07-31-2020, 11:43 AM   #6
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Hopefully a good fit between intake and head will fix your problem.
Do the plugs smell like gas? I ask because I think an intake leak would result in a lean condition, not rich.
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gasket, low rpm, manifold, mercruiser 3.0l, stalling

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