I had a similar situation when I replaced my water pump rubber piece but didn’t replace the housing. It seems that when I would get to a higher rpm it was starting to overheat. I don’t know what actually happened to fix it but I replaced the pump and housing the second time and never had a problem again.

I ran another test last night...

I replaced the water hose from the transom to the pump. Started engine with the hose off the inlet into the manifold... good water at idle. Bumped to 1200 RPM, good water. Bumped to 1500, good. Bumped to 1800. No water. Brought back to idle. Still not water. The only way to get water was to shutdown the engine and restart.

At lunch I'll connect the garden hose to the inlet of the pump and see what happens.

Any thoughts on the above?

Thanks!

Yes.....same thoughts as before.


a. Sea pump housing, inspect or replace. A worn housing will lose pressure and volume at higher rpm

b. Transom water intake. At the very least remove the drive and fish something through the hole in the bellhousing to check for blockage.

I know that you have already flushed the system but what do you mean by that? I ask because it could mean different things to different people. I don’t know where you boat at but on the Missouri river where I do most of my boating it’s not uncommon to get corn husk and other floating debris stuck inside the cooling system and usually right at the oil cooler, when this happens you need to take the hoses off and flush them individually and not just a general run the water through from the thermostat housing. It’s worth a shot at this point.

Update...

Pulled the transom to pump hose at the transom. Shoved my garden hose down into it pretty good and fired it up. Removed the inlet from the manifold. I had good water at idle and no water back-flowing from the garden hose connection. Increased RPM to 1k... good water. Increased to 1500 or so and water was flowing then stopped. When it stopped flowing, water was gushing from the garden hose connection (not sealed but shoved about two feet in... definitely saturated the pump).

What would cause that? To me this would say the pump is the issue.

Running out of ideas. Impeller and housing??

At first I was hoping it was a problem with the exhaust... blockages, etc. Not the case. Everything is clean. Water flow from the inlet through the exhaust is good. The problem is ahead of the pump or the pump itself.

remove the hard hose from the impeller pump to the transom and inspect the inside or better yet replace it. Then remove your sea water pump and inspect the housing and impeller or better yet replace that too. If it is in good shape then you have a spare to keep incase you blow one on the water. Also, like suggested before remove the inlet hose of the oil cooler and get a mirror in there to make sure it is clear. Rather than inspecting one thing and trying again, then tearing apart again, check what people are throwing out there.

Did that yesterday (hard hose). Also inspected all the lines, cooler, etc. They're good. I guess it's on to the pump.

pump stops pumping. won't re start until you quit spinning it . it is the pump. check the impeller. it could be slipping on the shaft and stops turning at a certain load...

I'm confused, when I run hot the first thing I look at is the impeller, then the housing.....I am assuming this is the same for most boaters? I am not sure how you got steered in the direction to check everything else first