9.9 falters at high RPM

[Grant T]

I have a mid-80's 9.9 Evinrude that is in moderate condition - it does a lot of sitting at dock. It runs evenly up to almost max throttle, but will miss and gag at 100%. I think it's the high speed jet, but can't see an adjustment for it. What are the steps I should take to narrow this down.<br />Thanks, Grant in VT

 

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Re: 9.9 falters at high RPM

Drain the carb bowl to rule-out water. Then with half throttle while warm,piloted by someone else, try to adjust the idle mixture screw, as you may be too lean. Before you do this tho, turn the idle mixture screw in until it just makes contact with the seat,while counting the turns (DO NOT TIGHTEN), and write this number down.<br />I would start tweeking by opening (counter clockwise) the idle mixture by 1/8turn,and waiting 30 seconds. Do this,1/8turn at a time, waiting 30 seconds between adjustments,until it starts to stumble...Then, turn it clockwise 1/8 turn,and open up the throttle,and see if it straightens out..If not, try new plugs . If still no change in performance, it you may have to pull the carb and clean it good.<br />Also, if possable, peer into the tank to see if there is any water in the tank. Make sure the tank is venting too.