Details on how to check and adjust the float level on a four stroke outboard motor.

This is a great one that I don't see very often, but it will trip you up if you are not aware of it. Basically it is a low float level causing a lean mixture. This causes a high speed miss, or stumble or surging, usually at half throttle or more, but can be through the entire rpm range. It can also cause a poor quality idle, or an idle that slowly gets worse until the engine finally stops running. This is a 40 hp Mercury outboard missing, stumbling and surging at high speed, low on power. This problem is applicable to Yamahas, Mercurys, Tohatsu, Suzuki, and any other four stroke outboard motor with a carburetor, or multiple carbs. Because the float level is non adjustable on these carbs most people just put them together without even checking the float level. This video show great details on how to check and then adjust a float level.