50HP -4 Evinrude - 2 problems

[series2000]

'01 50HP Evinrude (Suzuki) 4-stroke on a pontoon - has a rev limiter in neutral (I think) to prevent overspeed without load. Recently I've been experiencing the rev limit in forward at the beginning of a run. Revs fine in reverse but bucks and shakes in forward for the first two minutes or so then functions fine. Any ideas?<br /><br />Second problem - overheat. Last year experienced a number of overheat warnings. Changed impeller (looked good) and changed the thermostat (pretty cruddy). Experienced another overheat on the fifth trip this year; idled for 40 seconds and cleared up for rest of the day. Could this be a faulty sensor? I want to avoid the diverter valve under the oil tank if at all possible 'cause it looks impossible to get to.<br />Any advise would be appreciated. (I love the motor otherwise)