Raw water cooled 2004 5.7gi-e overheats without wot

[Shark_bait99]

When I cast off I need near wot to push water into raw water system, or engine will overheat. I find it takes about 30 sec of near wot before temp gauge literally swings down to 150. Before that it was slowly climbing above 180. Impeller replaced 1 season ago. Without wot, engine would beep and cut out at 210. Once waters in the engine, im fine for the rest of the day.
Thought of priming engine with water through the hose but I suspect it would leak out. no clogs visible on the inlets of the leg. Any other common suspects or is this normal?

[Shark_bait99]

The po told me it was an airlock in the raw water system.

[86 century]

I think I would try a new impeller

[skydiveD30571]

You only need to overheat once to ruin an impeller. Doesn't matter how new or old it is. I'd start with changing it out.

[Don S]

Sounds to me like you have a slight air leak on the inlet side of the pump between the drive pickups and the raw water pump.
Possibly the cap on the flush hose ??????

[dsiekman]

This happened to me when I bought my latest boat. Exact same scenario. Mine turned out to be a leak in the pump housing. While checking your impeller, remove the hose feeding your raw water pump and see if the inlet is plastic. If so, there is a chance that is your problem. I ended up replacing the whole pump though I have since learned you can buy just the housing (for about 1/3 the cost of a new pump). If you do have the plastic inlet, wrap the joint between the plastic inlet tube and metal housing with silicone tape and reinstall the hose. If that solves your problem, then it is time for a new housing.

[Shark_bait99]

Sounds to me like you have a slight air leak on the inlet side of the pump between the drive pickups and the raw water pump.
Possibly the cap on the flush hose ??????

Thanks Don, the flush hose cap has been removed and replaced several times, with the symptoms the same, so I don't think its loose. I will try some silicone tape to see if the cap is not sealed...

By drive pickups are you referring to the raw water intakes on the lower part of the leg?

If so, then my search should evaluate the lines through the leg which connects the drive pickups to the raw water cooling intake tubes? The reason I ask is that my leg is currently disassembled and this would be a good time to check. Is it possible to pressure test the cooling system with a rig functioning similar to the sticky on pressure testing the leg for oil leaks. After its reassembled, I would need to blocking the raw water outlet and seal the drive pickups, then find an appropriate place to apply pressure. The raw water pump system should be a closed system? Then a little soapy water and look for bubbles?

I am obviously too inexperienced to do all of this myself, but I think it would help to point the tech in the right direction. They seem to be fine with the repairs, just not as good at finding out what is wrong. Looking for a new tech but I am stuck with them for now. Anyone know a good volvo tech in Calgary???

Thanks

[Shark_bait99]

This happened to me when I bought my latest boat. Exact same scenario. Mine turned out to be a leak in the pump housing. While checking your impeller, remove the hose feeding your raw water pump and see if the inlet is plastic. If so, there is a chance that is your problem. I ended up replacing the whole pump though I have since learned you can buy just the housing (for about 1/3 the cost of a new pump). If you do have the plastic inlet, wrap the joint between the plastic inlet tube and metal housing with silicone tape and reinstall the hose. If that solves your problem, then it is time for a new housing.

Thank you. I will take a look into the housing as well. You and Don seem to be on the same page, as the housing and inlet hose are in between the pump and drive pickups.