my freind has a 4 or 5 year old optimax connected to a jet mounted in a motion marine aluminum boat. the motor will only start when the battery is very charged, (13.5 volts or higher). it will always crank over but will not start without these higher voltages, and still not every time. if it does not start it acts like it is starving for fuel, wants to go but will not stay running. if it does start it runs great as long as you dont turn it off. he has recently replaced the alternator and all 3 fuel pumps. the dealer says he cleaned out the vapor canister and the boat ran ok for a short time. access to powerhead is tough as it is droped in this hole like an i/o. i shoud add that he has an electric start honda kicker motor that is tied in with starting battery for the optimax. he has used this motor while stuck to charge battery back to 13.5 so he can get home. any help will be greaty appreciated since i am an omc guy and do not know mercs. thank you all for your help. keykev................