Westerbeke Raw Water pump not pumping

The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.

SeaDogAK

Senior Member
Joined
Aug 9, 2021
Messages
356
Vessel Name
Sea Dog
Vessel Make
1991 DeFever 49 RPH
I have a Westerbeke 8.0 BTD generator, which I believe is original equipment in my 1991 boat. Last summer I stupidly ran it with the seacock closed, which chewed up the impeller. The impeller bits clogged the heat exchanger, and when I tried to rod them out I realized the heat exchanger was totally clogged with scale. I changed out the heat exchanger, but now I’m only getting the tiniest trickle of water out the exhaust.

By pulling hoses I’ve isolated the problem down to the raw water pump. The hose going into the pump gushes water, but only a tiny trickle comes out of the pump. I’ve changed the impeller twice, but that’s not the problem. I can see the shaft turning inside the pump housing, but it’s not moving any water.

A new raw water pump is over $500. Does anybody have any ideas about troubleshooting or fixing the old pump, or do I need to bite the bullet and replace it?
 
Crank the engine with the pump cover off and see if the impeller is spinning. The shaft key may be missing or broken. Also I have had the center hub break free from the rubber part and spin free.
 
Last edited:
Do what Archie said. If the impeller turns at the same speed as the shaft, look for wear on the end plates and the cam.
 
Thank you, I will try that once I can get a helper to the boat.
 
You probably just need to change the impeller.

The pump impeller on the Westerbeke 8kw has a pin (actually a small threaded rod) thru the center of the shaft hole which mates with a slit in the pump shaft. It's not that uncommon for the pin to completely come out of the impeller. This allows the shaft just to spin in the impeller.

Open the back of the pump and pull out the impeller. Compare it to a new impeller and you will see the problem.
 
You probably just need to change the impeller.

The pump impeller on the Westerbeke 8kw has a pin (actually a small threaded rod) thru the center of the shaft hole which mates with a slit in the pump shaft. It's not that uncommon for the pin to completely come out of the impeller. This allows the shaft just to spin in the impeller.

Open the back of the pump and pull out the impeller. Compare it to a new impeller and you will see the problem.

I’ve changed the impeller twice. That’s definitely not the problem. The pin is in the slot in the shaft.
 
Sometimes the broken pieces of impeller settle down by the seacock. When the new impeller starts sucking water, the old pieces flow upwards to clog the flow of water.
 
I’ve also found a broken vane stuck in the discharge port of the pump casing out of sight. With the impeller removed, stick something flexible up the outlet hole probing for broken bits.
 
I’ve also found a broken vane stuck in the discharge port of the pump casing out of sight. With the impeller removed, stick something flexible up the outlet hole probing for broken bits.

Yes! I pulled the impeller again and probed the discharge port and it was COMPLETELY stuffed with rubber bits. Cleared them out, rechecked the new heat exchanger to make sure no bits worked their way into it, and I have strong water flow out the exhaust. And no leaks so far.

I guess the moral of the story is that a raw water pump is a very simple piece of equipment. If the impeller is intact and turning, it has to pump water. If it doesn’t there is a blockage, and it’s just a matter of finding it.
 
There was someone either here or on cruisers that put a basket strainer after his pump and before the heat exchanger to catch impeller parts and provide a visual check. Probably not a bad idea.
 
Another reply mentioned the cover. If there's a clear wear line at the outer perimeter of the cover, there's a good chance the cover is worn. The impeller must seal on the cover as well as the opposing housing surface in order to pump. Too much clearance and it loses most of its capacity. Most covers can be flipped to get longer life. Even if there's writing stamped on the surface, it can still be better than a worn face. If the inside face of the housing is worn and you don't want to spring for a new pump, you can cut a piece of stainless shim to create a new surface for the inside of the housing. Put it behind the cam to cover much of the edge. That can keep you going if you're out of reach of parts and you really need that pump to work! Pump covers are an easy spare part to inventory. Spare pump is really useful, as well! :)
 
Last edited:
Yes! I pulled the impeller again and probed the discharge port and it was COMPLETELY stuffed with rubber bits. Cleared them out, rechecked the new heat exchanger to make sure no bits worked their way into it, and I have strong water flow out the exhaust. And no leaks so far.

I guess the moral of the story is that a raw water pump is a very simple piece of equipment. If the impeller is intact and turning, it has to pump water. If it doesn’t there is a blockage, and it’s just a matter of finding it.

Yes!:dance:
 
Sometimes the broken pieces of impeller settle down by the seacock. When the new impeller starts sucking water, the old pieces flow upwards to clog the flow of water.
I had an impeller shred itself after running for an entire weekend. The pieces were in the raw water pump, the hose, and the end cap of the heat exchanger. Took about 2 hours to clean out and replace impeller, but clearing the hose and heat exchanger were the hardest part.
 
Good day
You might want to try a Kabota dealer , I got raw water pump to fit mine 68$ Canadian plus gasket
 
I have a Westerbeke 8.0 BTD generator, which I believe is original equipment in my 1991 boat. Last summer I stupidly ran it with the seacock closed, which chewed up the impeller. The impeller bits clogged the heat exchanger, and when I tried to rod them out I realized the heat exchanger was totally clogged with scale. I changed out the heat exchanger, but now I’m only getting the tiniest trickle of water out the exhaust.

By pulling hoses I’ve isolated the problem down to the raw water pump. The hose going into the pump gushes water, but only a tiny trickle comes out of the pump. I’ve changed the impeller twice, but that’s not the problem. I can see the shaft turning inside the pump housing, but it’s not moving any water.

A new raw water pump is over $500. Does anybody have any ideas about troubleshooting or fixing the old pump, or do I need to bite the bullet and replace it?
Be sure that none of the impeller bits are lodged in the pump outlet fitting.
 
Back
Top Bottom