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Question
Do you know if a 1987 130hp 3.0 mercruiser that is ideling to fast can suck water back into the cylinder's on shut down ,and only just two of them or would it be in all four.
    Thank you robert

Answer
Hi Robert...Thanks for selecting the undersigned to respond to your question.

I'm not a mechanic by any stretch of imagination, but in my opinion, the only way fresh water could enter a cylinder is if the cylinder wall is fractured and there's a crack in a water journal in the block or head. Otherwise, so long as the fuel line is properly secured, there would be no way for water to enter your fuel supply, unless the fuel was contaminated. On top of the carb is an air filter and a flame arrestor, which would prohibit any water from entering the carburetion system. Better check the compression on each cylinder, and then do a fresh water circulation pressure test on the block.

Safe Boating
Ron Blanchet