I recently purchased a 1995 Grumman pontoon boat with a johnson 50 hp outboard engine. The engine looks really clean and has no trouble turning over, but will not start without manually pumping the throttle, and once running will only remain running with throttle pressed. The engine will not idle, but just dies when throttle is released. I have changed spark plugs with no change in results. I have tested for spark with and it passed. Any advise on next step? Can I clean the carbs while still on engine or do I have to take them off?
