low rpms

[donhelp50]

I have a 1988 85 hp force on a 17' bayliner trophy it will only turn 4600 rpms at full throttle with 15" ss prop I have checked compression,spark,cleaned carbs and adjusted new fuel lines and plugs. should be turning atleast 5200 to 5500 according to manuel any sugguestions to problem.

 

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Re: low rpms

On the carb adjustment, check that the throttle plate is wide open at wide open throttle (this can be done with the engine not running). If it is, and you're sure all cylinders are firing, receiving fuel, and compression is equal and strong, go to a shorter pitch prop, or one like the original aluminum 15 that it came with. Or maybee borrow/rent one from a marina and test it.<br />Even tho its the same pitch, the original is not cupped (at least, i don't think it is), and the dia may be smaller too...Less blade, less thrust,more RPMs.