91 force 90hp tachometer setting

Sir44

Cadet
Joined
Jun 24, 2015
Messages
7
hi
I put a 91 force 90hp on a boat that had a 115hp merc. The tachometer in the boat seems to be reading way to high. The tachometer has a dial on the back with about 8 or more settings on it. How do I set it properly? Or do I just guess? It says I'm running over 1500 rpm at an idle.
Thanks
 

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
The Mercury tach is a 12 pole tach. No matter what you set it to it will not read correctly on the Force engine. That is, of course, unless it also has a 12 pole-20 pole setting. Then set it to 20 pole. And, of course, this also is contingent upon the Force NOT having a Mercury ignition.
 

Jiggz

Captain
Joined
Oct 23, 2009
Messages
3,817
If it has a 20 pole setting set it to 20 and try it. If you want to verify its accuracy then you should get another speed tach or get one of those laser/infrared tach from evilbay.
 
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