Hi, I have a 9.8 1972 merc which I use as a trolling motor, problems I'm having is from the pee out let I'm getting some water and a lot of smoke, after running for about 1/2 hr the engine just dies like as its over heated, I had replaced the impellar 3 months ago and it seamed to work OK but had noticed that there was a small rubber seal at the top of the drive shaft, it dosent mention this in the manuel, also can't find the thermastate to check, any help would be most welcome