my 115 hp (1985) yamaha enging oil tank was overflowing into the lower carb.after checking the engine oil tank float switch along with the main oil tank switch i found that i had a bad control mod.after replacing that unit my system now works fine..while all this checking was going on i was wasting a lot of high dollar oil,so i came up with a better way..i used a lgt.of fish tank airator hose the same size as the overflo tube on the engine oil tank and routed it back to the main oil tank drilled the correct hole in the top of the tank now any over flowing goes back to the main tank not into the carbs...................try it and save some oil bucks.....works for me.....