"water out the exhaust tube"? What do you mean? Where, out what exhaust tuble? Water goes up the waterpump tube - I don't know what you mean by "out the exhaust tube". I do not know of any other tube.

Help me here. Are you sure it is overheating? How do you know? Some motors just don't "spit" much water out, but they cool fine. If it is overheating then based upon what you have already done, I'd say it is time to pull the powerhead and check for a blockage. Years ago we sold a brand new 4hp and it overheated. We checked everything. Couldn't find a problem. Finally we pulled the powerhead. There was a flake of plywood blocking the water intake passage into the powerhead. It came from the plywood base that the powerhead was bolted to when it left the assembly room at the factory. We cleared the blockage and the motor was fine after that. A longshot, but if you've checked everything else.......!!?!!