Hello Everyone, I recently purchased...
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07-26-2020 08:49 AM
Hello Everyone,
I recently purchased a 1989 340 Sedan Bridge. The boat is in great condition and runs great but I notice that the starboard engine burns about 1 qt of oil every 4-5 hours and it also consumes more fuel than the port side motor (it takes it a bit more throttle to run it at the same RPMs as the port side motor). Some people told me to use marvel mystery oil, others said that is nothing more than snake oil. Is this common for two identical motors (Mercruiser 7.4s) in a boat to perform differently even though they have the same number of hours on them (1,200)? Is there anything I can do to help this motor (without rebuilding it)?
Thanks,
Joe
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08-02-2020 05:53 AM
Stuart
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09-09-2020 04:12 PM
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09-15-2020 06:51 AM
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09-15-2020 08:25 AM
The compression check is a good starting point. Oil consumption is either blowby in the pistons, leaking past hard valve seals or external oil leaks. The external is easy to spot.
If the compression check is good, then it is possible to swap the valve seals w/ limited disassembly.
If the measured fuel consumption is more, then compression is also a good starting point. Assuming a carburetor engine, so the carb should be clean and properly adjusted.
The throttle cables need to be adjusted properly.
Indiana, welcome to the forum. Yes same solutions.
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