40 hp mercury force slow cranking while plugs are in.

by jeff nolin
(jacksonville nc)

I have a 40 hp 1996 mercury force outboard that will hardly turn over. If I take out the plugs she spins like mad. I have checked and cleaned all connections and even switched out the starter. I bypassed all components just to make sure. I have never seen this before. Im beginning to think its an exhaust problem but not sure how to check. Any help will be appreciated.

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May 30, 2014
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same issue here
by: Anonymous

I have another 97 40hp merc/force with the same issue. Did you find anything out about it?

Jan 19, 2014
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hard to crank
by: Zuke

This is just a thought I use to work on a lot of Johnson and evinrudes, not sure about mercuries, but some of them had a compression release on the top of the motor so that when you cranked it it would release some of the compression to let it turn over a little easier, look around on your motor and see if you can find something like that or check your manual about. like I said just a thought, I may be totally wrong about it.