After chasing around after high engine temp problems, and replacing senders, thermostats, wiring
, etc.. on more than one engine, I have found that most of the time the problem was with the areas mentioned by other posters with poor coolant
flow being #1.
The wiring has nothing to do with controlling engine temp. The fact that your coolant
flow seems adequate at low RPM
, but not at higher RPM indicates strongly
that you have a flow problem. The first and easiest things to check are the hoses (which can look fine but are collapsed internally), strainers, and your pump
impeller(s). Dive under the boat
with a mask on and make sure your intake isn't clogged with weeds.
If all that looks OK, then you need to get after the harder to fix stuff. Clogged heat exchanger
, mixing elbow
, and the cooling
passages inside the engine.