Universal M18 raw water pump issue

[drh1965]

So the original Oberdorfer pump start leaking out the weep holes. It is a 202M15. I replaced it with an N202M15. These are supposed to be interchangeable. Good news: the leak is gone. Bad news: the new pump is seemingly much weaker than the old. There is much less exhaust water now. The engine is also running hotter. Any ideas? The impeller seems fine...

 

[Skipper]

The shaft might not be fully engaged. I can't recall exactly, but there is something with the shaft on the older universals that requires great care when installing the raw water pump. Check the documentation closely.

-Or- It could be a coincidence, and you've suddenly got a blockage downstream. Check the HE.

My M-18 doesn't throw much water out the back either. But it runs cool. I even have the small HE, and it's original 30 years old, still runs cool. I keep it clean and RR the zinc.

By the way, a good-looking impeller might still be bad. If the pump sat on the shelf for awhile, it could be stiff. I'd buy a replacement and try it, then keep it as a spare if that aint it.

 

[pogo2]

check intake hose

I had an issue similar to yours, I found the water intake hose to the pump clogged with seaweed, it would allow just enough water to flow thru so you would think the cooling system was working fine. If you have a sea strainer check the connection hose from the hull to the strainer, the strainer, then the hose to the pump :neutral:

 

[drh1965]

Thanks for the replies. The thing is, I was running the engine just before I swapped pumps and all was fine. I swapped the pump, and the weak flow started... I suppose it is possible that something got in the system after the swap but that would seem like a hell of a coincidence. With my luck, LIKELY! I did check the hoses, but something could have gotten into the HE. Maybe closing/opening the raw water seacock broke some crap loose.

As to the shaft, it does not seem possible to put the shaft in the wrong way...

I guess I'll have to put back the old pump again and see if things are back to normal. If not, I guess I'll take off the HE and backflush it.

Why do simple jobs cause me the most grief? Ugh.