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Author	Topic:   mercury 225 compression
brybasack	posted 09-23-2005 11:08 AM ET (US)         I have 1995 twin mercury efi's.. the compression is 95lbs across the board..should i be worried about the powerheads?? I still have some offshore fishing this season??help
bsmotril	posted 09-23-2005 11:48 AM ET (US)             No, that is fine. As long as they are consistently the same across all the cylinders, within 10%. You'll get a lot of variation in the actual compression reading depending on how you measured it. The right way to do it is remove all the plugs to get good cranking speed. Then, open the throttle to the full open posisition, and crank through until the gauge quits moving up. Most people don't open the throttle, and that can make a motor with 125 lb compression read anywhere from 80-100. The bigger block motors are pretty low, around 7-8:1. So your reading is fine. BillS

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