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Ask Dominick Your Own Question
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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I have a 1969 johnson 9.5. i rebuilt carb. several months back.

Customer Question

i have a 1969 johnson 9.5. i rebuilt carb. several months back. ran great. next time out ran bad...low rpm good.... high rpm not good.... seemed like starve for fuel... could make it run ok (not great) with squeeze bulb. put new fuel pump on and runs ok low rpm but not good at high rpm. Here is the crazy part!! At higher rpm it now begins to choke(Load up)... if i pull the cover off the motor it will rev up and run good!! put cover back on while its running it loads up and stalls out....pull cover (while still running but choking) and it revs back up and runs great. i have pulled insulation from inside cover to make sure it was not being suck into intake... its all clear. Is this some sort of pressure build up under cover from leaking gasket or exhaust?? What should i do? tim
Submitted: 2 years ago.
Category: Boat
Expert:  Jeff G. replied 2 years ago.
You are getting exhaust fumes in under the cover and this exhaust interrupts the proper air to fuel ratio. Check the rubber seal #312211 on the exhaust housing is intact and in place. It goes around the midsection exhaust housing. The other common place for exhaust problems is the gasket under the powerhead has failed or even the exhaust housing to powerhead may have corroded again letting exhaust fumes to escape. These are the three most common places the fumes escape.Check these out and get back to me which is leaking. Once sealed I think it will solve your problem.Thanks

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