Yamaha 50 '96 model

[<Striper Guy>]

Yam 50 on a 24 ft. pontoon. Had motor serviced in March, hasn't run right since. Mechanic checked again and said he adjusted timing. No help. Idles rough and won't run over 9 mph. I'm going out to buy a shop manual and work on it myself. Hasn't been run much since last November. Any suggestions on where to start?

[<boats.net>]

It is hard to say, You need to start with the basic. Check compression, check ignition to see if lost fire to any of the cylinders. Check fuel system, squirt gas in carbs while running to see if picks up rpm's if so it is running lean, pump primer bulb while running if makes it worst then fuel pump diaphram damaged.