1987 85hp Force outboard idle questions

Jiggz

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Joined
Oct 23, 2009
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Well, it seems she is running but you still need to tune her up. First, make sure you are using the proper plugs and are not fouled (BUHX or UL18V, I prefer NGK's). Adjust the idle mixture screw (which is only set at an initial 1 turn out) by slowly turning it counter clockwise (CCW) until the engine starts to bog down due to over rich mixture, mark the position and then slowly go the other way (CW) until it starts to bog down again due to too lean of fuel mixture, mark the position and then finally set the screw at midpoint of the two previously marked positions.

If hole shot (getting up and going on a plane) is poor you can always open the idle mixture a little bit to improve it (but usually no more than 1 1/4 ~ 1 1/2 turn out). Be careful though, too much idle mixture can foul plugs and there is a diminishing return with too rich of fuel mixture.

With engine off and carb covers (all) removed, place the control lever in full forward position. using a flashlight verify all three throttles are in full horizontal position (relative to the carb's body). If not, adjust as required.

With proper tune engine will idle smoothly, 900~1000 rpm in neutral and 750~800 in gear.
 
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