I have twin 1999, 150 Yamaha outboards, Model S150TXRX. One of the engines runs fine, the other sounds fine but does not have much power on its own. When I throttle up it loses power under load. With both motors running, the problem is not noticible and boat gets up to speed. Starboard motor can get on step alone, port motor cannot. Change spark plugs and fuel/water sparators. Any Ideas??
