Volvo 4.3GL-C overheating when first put in the water

[ZX10R]

I am trying to help a friend with his boat he has a 2004 Regal with 4.3GL-C engine and Penta SX outdrive. The first time he used it this year it overheated he took it to a marina and they replaced the raw water pump. Now when he first dumps the boat in the water off the trailer it will overheat but if we can hurry up and get the boat up and running across the lake it will cool back down and run fine the rest of the day. It acts like the pump won't prime at idle you have to get going for the water to be forced up into the raw water pump. Once the pump is primed he can run it all day even idle and the engine stays cool. Anyone have this issue and can help me out here?

Thanks

 

[spoilsofwar]

The water pumps on these engines and drives don't "prime", because they are located below the static water level. As soon as the boat is in the water, there is water at the impeller. In other words, they don't "lift" water.

The problem is something else. I would pull the pump housing and inspect the impeller; I realize it was just replaced but that doesn't mean much if it wasn't done by you. Backflush the water intake hose that attaches to the transom and verify its clear. Pull the thermostat housing and inspect it internally, and the tstat itself.

 

[ZX10R]

I will have to take a hose out with us next time we go and check the static water level. Last week I took the water pump apart, hoses off, pulled thermostat, and back flushed the system couldn't find anything major wrong. I did find some pump fragments stuck in the thermostat housing and removed those. I understand these pumps don't lift water but what I can't figure out is why water isn't getting to the pump at idle. Once you get water to the pump (faster then idle) it works fine.

 

[spoilsofwar]

Pull the water inlet hose off the pump while the boat is in the water (be prepared to plug it or lift it above the water line). There should be water coming through it, engine off.

 

[ZX10R]

K thanks I will try that