hotter than normal running temp

I've been working on a similar problem. Sounds like you may not be getting enough water flow. Could be some blockage in the water lines, maybe impeller parts from a previous impeller that broke apart? Also, could be caused by air leaks - check all hose clamps for tightness. Check the water strainer (i assume your boat has one) - make sure it has no cracks, the o-ring is good, and it's install back good and hand-tight.

Just some thoughts and ideas I've picked up from others and have tried myself.

FYI...there's a flow test you can perform which might be helpful. I picked this up from skidim.com - run a hose from the impeller pump to a 5 gallon bucket. It should fill the bucket in 15 seconds when the motor is running at 300 rpm. I did this and it was a nice task to prove the pump was pumping correctly. If you're doing this out of the water, make sure you have a good supply of water to run the motor at that high rpm for that long. I ran a hose from the raw water intake to a second 5 gallon bucket, filled 5 gallon bucket with water and stuck a water hose in it. When I did the test, the motor sucked that bucket almost dry in 15 seconds.

Good luck.

Correction - that should be 3000 rpm (not 300).

My boat was doing that when I first bought it & replaced the impeller. I thought I cleaned all the water lines out . At a fast speed old impeller fins were being pushed up to one spot making like a huge clog. I found around 15 big pieces in the main water hose that starts after the oil cooler.You really need to remove all the hoses and clean them out.Looking into then doesn't work cause there hard to see and most off them are in the middle when your not running. Little pieces were also found in my thermostat. My oil cooler also had a leaf or two in there .Definatly check all those areas and that long water hose. Let me know what you find . Dan