hi , i'm working on a 1999 40 hp yamaha . model # c40tlrx. my question is about the fuel enrichment system. what would be symptoms of a faulty solenoid ? or a ruptured diaphragm ? also on this model, what position should the manual valve be in ? (open or closed ) the owner brought the boat to me complaining about a lack of power, engine shutting off, and hesitating . i did the usual preliminary checks (compression and spark gap ) all good. i then tried to crank the motor to see how it was running. it would only fire up for a second and only at idle. after playing with it for awhile i found the manual valve on the fuel enrichment. i turned it and the motor cranked but ran pretty bad. i then contacted the owner to see if he had turned the valve . he said that he didnt even know it was there. so i thought the carbs were stopped up and that it was now running off the enrichment valve. so i went through the carbs. they were very clean. the slow jets were partially clogged. after reassembly the motor runs better but still not smooth and is smoking alot. i didnt see any problems with the diaphragm. just not sure how the system works. any comments are welcomed. thanks......david