1970 9.8 carb adjustment

I finnally got the new coil on the ol' girl and she started right up, running on both cylinders. I idled down low and smooth, but I couldn't stop there. I thought I would tinker with the idle mixture. I "assume" its the screw that is to the right of the carb opening that's recessed in a cylintrical hole. If so, when I turn it counterclockwise the I dle goes up past the rpm I think it sould be. I just want to be sure that is the mixture screw. If it is I will need to find a way to set the idle down when I get the adjustment right. I have never run this motor, I bought three of these motors and built on good one from parts. I may not have gotten the throttle contol lever in just right or something. I am a 25 yr auto tech but a novice outboad mechanic to say the least. Any input would be great. Thanks, Chris

Re: 1970 9.8 carb adjustment

It's the idle mixture, typically 1 to 1-1/4 turn out. Make sure the throttle butterfly shuts all the way. Outboards are strange that way. There's a hole in the butterfly to allow a predetermined amount of air to achieve idle speed, so it's not really adjustable like you're used to. Idle speed is actually adjusted by timing on American-made outboards. Every other gas motor on the planet uses a screw to adjust the butterfly and therefore the idle speed. Go figure.

I should also mention that you're not looking for a smooth idle. That's too lean and it'll bog on acceleration. It has to be 1/8 - 1/4 turn richer than that. That's pretty typical of all 2-strokes.

Re: 1970 9.8 carb adjustment

Ok, did not run the motor tonight but the throttle was not closed with the twist trottle at full slow. I may have done wrong but I backed off the set bolt that stops the linkage not the one on the carbs butterfly shaft. I adjusted it to where it just made contact with the tappered "fange" looking slide that opens the butterfly. I know this adjustment tetarded the timing at idle. Did I do the right thing? Also I set the mixture screw at 1/12 turns out.