cooling system help

[almost perfect 2]

I have a westerbeke 10-2, diesel inboard. It is cooled with both fresh water and sea water.
the intake for sea water (thru hull) has a sea cock that can be shut off and another valve above it in the boat with a hose attached that should suck water . when I ran motor with the hose in bucket it did was not pumping water out of the exhaust. Last year while in the water it worked fine with the thru hull suction?
I closed the thru hull valve and opened the one with the hose attached.
did not want to run it for long with no water running out of the back.
can anyone offer any suggestions or help?
Thanks

 

[dparilla]

When was the impeller last changed?

it could be as simple as insufficient water pressure by only have a bucket full of water (it will take longer to prime without that head of pressure.) But, I would check the impeller. Before going much further. They can freeze up in the off season and break apart when you try to run the engine in the spring.

 

[Pat]

When you say another valve above the thru-hull I'm confused...we have a 272 LE that has the thru hull w/ one handle....when handle is turned in the spring, i.e. opened, the water flows into the water pump/ via an impeller, then into the heat exchanger, this as soon as the engine is started. Separately, there is the little reservoir in the lazarette
that is part of the on-board cooling system separate from the water brought in thru your open thru hull.....I agree with dparilla that you should change your impeller..my first one lasted 10 years...my 2nd thru 5 or 6th seems to lose blades faster which I have dug out of the water pump hose and I'll bet there are blades in the heat exchanger as well.....I don't have the nerve to try and remove the heat exchanger as I am not good with that sort of thing, but reading on these blogs, I think my heat exchanger should be cleaned.by someone competent..the boat is 27 years old...but I do have a decent flow out the stern and the engine does not come close to overheating. Does yours?