80 70hp yamaha -carbs just cleaned engine run great at idle and higher rpm-took it out today for a test ride after 5 min buzzer came on and the engine did what its suppose to do-run no higher than 2k-engine was hot-water comes out of the exhaust but the engine runs clean-my question is -is there maybe a bad gasket on the outer and inner exhaust plate that might be letting water pass into the exhaust which in turn drops stops the water from circulating inside the head-then it overheats?