I have a 1995 Johnson 25 hp, 2, cycle. The motor runs, but then after stopping or running it at a slow speed for a short time the motor will not run above 3 mph. When I attempt to throttle up the motor, it sputters and shakes. Then, intermittently it will throttle up and run fine, but then the problem comes back. Additionally, when it this problem is happening the motor is emitting more smoke than normal. Can anyone please help?