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How to COMPLETLEY drain AQ120B raw water pump during freezing months

D

DKaiser

Contributing Member
AQ 120B/270

I operate my boat throughout the winter months, I always drain the:


  • Manifold (manifold drain plug and copper line from heat exchanger)
  • Drain plug at the bottom of the heat exchanger
  • Loosen and open the face of the raw water pump to drain

Recently, I came to find my impeller had frozen earlier this winter causing damage to impeller, seal, and coupler and a jumped timing belt upon subsequent startup.
I am diligent about draining this system, it's a ritual. I suspect there was a minimal amount of water left in the pump to freeze the bottom impeller fins. How can I ensure there is no water left so I can operate throughout freezing temps?
 
Just loosen the two flange bolts on the pump and it should drain out. It wouldnt hurt to get new rubber gaskets for when you put it back together. How old is the impeller? Just pull the pump and get a new impeller kit and install it when you go to put it back into service.
 
Last edited:
kimcrwbr1 said:
Just loosen the two flange bolts on the pump and it should drain out. It wouldnt hurt to get new rubber gaskets for when you put it back together. How old is the impeller? Just pull the pump and get a new impeller kit and install it when you go to put it back into service.
Click to expand...

The impeller is less than a year old. I've done the R&R before, it's easy.

I don't see how loosening the flange bolts would allow the pump to drain completely as the inlet/outlet water lines enter above the lowest part of the pump. I have always been told to loosen the four face bolts rather than the inlet and outlet flange bolts - ? Either way, there remains a small amount of water in the bottom of the pump that seems freezes.

Raw water pump.jpg
 
The small amount of water in the pump should not hurt anything. Loosen the four cover bolts if you want either way you risk developing a air leak unless you replace the gasket.
 
Just got an old Trophy with a 250B. Haven't got it running yet but have been thinking about the same issue. If I remove the cap on the heat exchanger I can see the opening down to the pump. Seems to me a person could pour a bit of antifreeze down that opening to prevent freezing and maybe even lube the pump a bit while it sits. Bad idea? Good idea?
 
kimcrwbr1 said:
The small amount of water in the pump should not hurt anything. Loosen the four cover bolts if you want either way you risk developing a air leak unless you replace the gasket.
Click to expand...

The OP said he always opens the pump cover, but still had damage.
I'll bet his engine is tilted up in front, and some water stays in.
I run antifreeze through (on land) so any small amounts of liquid remaining after draining will not freeze

On the water, can you use the environmental safe antifreeze or Vodka.
Also on that model, I think you can pour the mix into the strainer and the pump should completely fill as there is a small bypass on the impeller.
 
Thanks Dennis. I had recently thought about the angle of the engine and believe that could be part of the problem. I will be running antifreeze through from here forth as well.
 
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