Compression ?

[crashj]

Five cylinders between 110 and 115psi one at 91psi. Noticed a 5-600 rpm drop. Time to rebuild power head or should I be looking into a remanned power head? 1999 200 opti

[EuropeanAM]

Please see the Sticky at the top of the forum, and provide your engine serial number when posting. Thanks!

Was the compression test performed EXACTLY as described in the below link?

http://www.bbcboards.net/mercury-3-l...ml#post2534330

If not... back up and do it as shown.

[crashj]

Short answer is no. Not warmed up and no water supplied but
everything else yes. My concern is the high difference in the last Cyl tested. Did that Cyl twice not liking the first result. Would testing five cyls drain the battery enough to make a difference?
the boat is now in storage till spring I guess this will wait until I can test run it and then retest properly. The reason I did the compression test before storing it is because I had noticed the drop in rpm at wot the last few times I had it on the water

[EuropeanAM]

A weak or discharging battery could definitely cause this.

Easy enough to confirm... fully charge the battery, and start with readings at the other end.

Same of similar results- there's a problem in the engine.

BTW- NEVER spin the engine over without water. Water pump damage happens very quickly.

[crashj]

Thanks for the info. Will definately follow your instructions when I get it out of storage. Will probably get it out early in case it needs work