Originally Posted by
gcnettl
Ok, so you changed the impeller, to no avail.
Your thermostat could be not opening, or not operating properly.
If you take the outlet hose off of the impeller housing, while your boat is in the water, and then crank up, it should throw some water out of that outlet.
While running, do you notice any play in your water pump? That is a good bit of hours on one water pump. It could be not pumping well after this time.
It really sounds like the thermostat or the water pump.