My 1990 90 hp Yamaha is having trouble idling. It has been getting worse over the past year. At he end of last season I had the carborators cleaned, and it idled well for a few outing. Now it hesitates and dies occasionally at 800-1000 rpm. High speed and even fast idle are fine. Any suggestions?
Have the fuel pump check. If thats ok have them pull the carbs. and check them to see how clean they are. If that all checks out have them look at the reed valves while the carbs are off.
MXA,My 1989 did the same thing a year ago, motor would stall when engaging gears, especially when water skiing. I purchased the Yamaha service manual (highly recommended) and performed a decarb, new plugs, carburetion and timing adjustment, oil pump check. I also changed the fuel hose as the rubber was starting to get hard and the water pump. The manual is a must and everything is straight forward with basic tools and timing light!!!The motor now runs great all the way from low idle to WOT.
1990 90hp Yamaha idles rough and dies
My 1989 did the same thing a year ago, motor would stall when engaging gears, especially when water skiing. 
Linear Mode
