Heat exchanger Question

[Chschaus]

While winterizing the engine this weekend before the boat is pulled I noticed a drip from the Obendorfer Fresh water pump. I am assuming it is a seal gone bad. I am planning on replacing the pump as it is the original that came with the boat. While I am at it I plan on removing the heat exchanger and giving it a good clean ( acid dip ) and inspection.
while this is off does the cooling system need to be drained of antifreeze? I plan on doing this over the winter.

 

[Mr. Scarlett]

Might as well go all the way, in my opinion. Make it a complete cooling system refit.

 

[Second Star]

It is possible to refit the pump with new seals. The shop would ensure the shaft is free of defects and insert new seals sized to the "shaved" shaft and a new impeller. Cleaned and repainted it too. This cost me about $500 in Canada 3 years ago, less than a new pump. Might as well replace the hoses too for about $50.

 

[Kenneth K]

..while this is off does the cooling system need to be drained of antifreeze? I plan on doing this over the winter.

Pulling the raw water pump does not affect the antifreeze level. Pulling the heat exchanger does (2 of the 4 HE hoses are anti-freeze inlet/outlet).

There is a usually a block drain petcock on the lower part of the engine (stbd side on M-25). You could drain the system here if you want to replace all the fluid. If not, just hold a jug beneath the hoses when you pull them off the heat xchgr.

 

[Chschaus]

Pulling the raw water pump does not affect the antifreeze level. Pulling the heat exchanger does (2 of the 4 HE hoses are anti-freeze inlet/outlet).

There is a usually a block drain petcock on the lower part of the engine (stbd side on M-25). You could drain the system here if you want to replace all the fluid. If not, just hold a jug beneath the hoses when you pull them off the heat xchgr.

Thanks Ken, I know the raw water pump doesn't affect the antifreeze. Not sure why I included that part of the project in my inquiry.
Was curious about the coolant system as I am not sure I want to leave it drained over the winter. I'll probably plug the coolant hoses while I clean up the heat exchanger and flush the system in the spring when all is replaced.

 

[Kenneth K]

I am not sure I want to leave it drained over the winter.

I've only had one experience with this, but I wouldn't recommend it. I had my coolant partially drained when removing the exhaust manifold (for the old alternator bracket swap out). It was partially drained for 2 or 3 months. When I later pulled the fresh water pump, the pump vanes had rust marks above where the coolant level had been.

 

[Ralph Hewitt]

While winterizing the engine this weekend before the boat is pulled I noticed a drip from the Obendorfer Fresh water pump. I am assuming it is a seal gone bad. I am planning on replacing the pump as it is the original that came with the boat. While I am at it I plan on removing the heat exchanger and giving it a good clean ( acid dip ) and inspection.
while this is off does the cooling system need to be drained of antifreeze? I plan on doing this over the winter.

 

[Ralph Hewitt]

What acid do you use?

 

[shard7]

What acid do you use?

I just did this for my Atomic 4, used full strength muriatic acid to clean the heat exchanger. Rinse thoroughly and use a baking soda solution to ensure the acid is fully neutralized.

Since removal of the heat exchanger requires draining at least some of the coolant you might as well do whatever servicing is warranted on the freshwater side while you're at it. I replaced all of my cooling system hoses and both impellers while everything was apart and easier to work on. Very glad I did because it led me to discover the raw water seacock barb that was on the verge of sinking the boat, and a missing vane on the freshwater impeller (which had lodged itself in the pump's outlet elbow).