I have been trying to figure this thing out but having trouble, before the boat would start up and run, only problem is it ran very very slow. I checked the compression, it was good. One of the plugs was not sparking much, replaced both plugs, the boat ran faster, but not much. When I put the muffs on after I changed the plugs, it let me rev it all all the way, before it wouldn't pass a certain point. Sorry I dont have a tach, I am going just by sound. Like I said its faster, but not as fast as it should be. Could this be a fuel problem? and does anyone know what the fuel mixture should be for this engine? Its on a 67 15ft 6in woodson tri-hull. I want to finally have a boat to fish on, but I am close to giving up. Any help please..