Water pump leak

[ItalianAngler]

I believe my water pump housing is leaking, yes I've seated the gaskets right, and used a gasket sealing grease. The motor will throw the overheat alarm if at trolling speeds for too long. There is some water in there when I drop the lower. This is a new lower unit, my only thought as of now is that the two pins that are used align the pump are sticking up too far. They were very hard to get into those holes, which i could tell were freshly machined. This is a remanufactured Yamaha unit, my original lower succumbed to a submerged object about a month ago. 2002 F225, exhaust stacks are new, t-stats are 2 years old.

Anyone encounter something like this? I was going to pull it all apart, and try to seat the housing down with nothing in the way, no impeller or anything like that to test the fit. Also, if I spray water down the tube carefully with a hose will it expose the leak in a fully installed pump?

I'm stumped here.

 

[g0tagrip]

I did have an intermittent hot alarm on my port engine at low or idle power. After all the other things we tried (t-stats, flushing,etc.) the problem turned out to be the impeller (bad blade). Put a new one in and no problems since.

 

[seasick]

Overheating at low speed can be a bad pump BUT if the overheat goes away when you speed up the revs, the more likely cause is a stuck open poppet valve. That is the standard test for a bad poppet.
The water pump housing is not completely sealed and can spit some water when running.
You can sometimes tell a weak pump by a weak telltale (pee stream). If the telltale is strong but the motor overheats, it's probably not the pump.