75 70horse johnson will not go full speed

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boat will get on plane but will not go full speed .should go about 45mph only getting up to 15 mph.boat sat for about 4 years .

 

[Joe Reeves]

Re: 75 70horse johnson will not go full speed

ArrorBurner..... Assuming you have compression and ignition on all cylinders, after sitting for that length of time, the carburetors are fouled, gummed, etc. The cure is to remove, clean, and rebuild them.