i have a 1978 johnson 70 hp that when i was running on the water it just lost over half of its power out of nowhere. when she is in netural the engine revs to the full limit. then when i put it in gear i get 40 - 45 percent power. i checked my filter, good, when the boat is running i squeezed the fuel ball and rock hard, the vent on my gas tank is open. dont know what else to do.