I have a 92 750 ss that runs great for about 45 min, then starts to loose all power. it's kind of stranger because the motor will never cut off it just will bog any time you give it gas. If I let it sit for a couple of hours and then try it again it's fine for about another 45 min. I've replaced the plugs, cleaned the carb, replaced all seals and diaphram in carb, flushed the cooling system, and replaced the fuel tank check valve. what could possibly be going on with this thing?