65hp with fouling plugs

[chris h24]

I have a 1975 65hp mercury 650 with a thunderbolt ignition. Serial# 4261467. The boat and motor have been garaged for the past 29 years and has approximately 200 hours on the engine. Last year I had problems with all three cylinders fouling. I could run full speed (38 mph) for 10-12 miles before the engine would start missing and eventualy it would bogg down. The motor ran, but my speed was maxed at 7mph no matter how much throttel I gave it. Please tell me where to begin.

 

[schaiss]

Re: 65hp with fouling plugs

Pull the carbs off and dip all the metal parts in card cleaner (a gallon costs $12 at any auto parts store). Dip metal parts ONLY, this stuff will destroy non-metal parts. Reassemble carbs and reinstall. If you are careful, you should be able to get the carbs off without ruining the gaskets (but they cost about $2.50 each), and with the age of your engine it would probably be a good idea that you have new gaskets on hand. If the fuel were allowed to remain in the system while it was idle for that period of time, replacing the fuel line and primer bulb would be recommended as well. Old fuel in the tank? get rid of it (use it in your lawnmower) and get fresh fuel.

 

[Chris1956]

Re: 65hp with fouling plugs

Chris, After you clean your carbs, also clean or replace the spark plugs, check the wires for arcing, pull the distributor cap and clean it, etc.

 

[Elmer Fudge]

Re: 65hp with fouling plugs

Have you checked to see if your T/stat is stuck open? if the motor is'nt running at the correct temp that can also cause the plugs to foul.