Re: 89 johnson 150 idle problem
A couple of things could be an issue. Engines idle slowest when deepest in the water-due to the backpressure in the water. If you tilt it up, there is less backpressure and the engine rpms will slightly pickup. Possible you need to sync and link the engine. If the carbs weep/leak any fuel into the airbox, the excess will accumulate at the bottom. When the engine is trimmed down, it will get sucked through the airbox drain hose into the crankcase #6 cylinder. Excess fuel can cause a temporary poor idle (smoking) till it consumes this fuel. Once consumed, it should idle normally. Remove the airbox cover and idle the engine in various tilt positions and see if you get any fuel dripping into the airbox. Poor idling can be caused by restrictions in the idle circuits in the carbs. Dried residual fuel can be a real problem in any fuel passages in a carbed engine. An aerosol carb spray is good to clean out these passages, and the rest of the carb passages as well.
