I'm going to change the impeller on my raw water pump before hitting the water, and a doubt popped to my mind.
How does the water in the closed cooling circuit moves around? Is there another impeller somewhere, which I should consider replacing?
Thanks in advance!

water pump in front of the engine driven by the serp belt,does not have to be replaced

Thanks for your reply.
Do you mean it doesn't require any kind of periodic check or maintenance?

Nope, it's a circulating pump, with no serviceable parts. with proper coolant it'll probably last a lifetime.

Paul, the raw water pump you are asking about is down on the bottom of the starboard side of the engine right behind the old style fuel filter that spins on if you have that...

It's serviceable by way of removing the belt and the pump. It uses a standard Bravo Impeller and o-ring kit. If the pump is scored badly, you may want to purchase the whole pump. Otherwise, it's an easy deal.

If you are referring to the closed cooling "circ pump", that is not serviceable and will last a long time. Mine finally failed at around one thousand hours and it just leaks from the wheep hole. It would be a tough fix in your boat. If it's not leaking antifreeze, leave it alone as you're fine.

Cheers!
jt

If your circ pump (closed cooling pump) every does fail, do not buy a standard automotive pump. The Merc pump has a totally different style brass impeller and it moves a much larger volume of coolant than the one from an automotive store. And of course, the one from Merc is about twice what they get from the Chevy Dealer. I think it retails for around $539.

Thanks guys, yep, it's the circ pump I was wondering about, 'cause I knew nothing about it.
For the raw water pump and its impeller, I already learned a lot from this previous thread !

496 takes a different impeller than those on the standard BBC bravo setups (454, 502, 500HP, 500EFI, 525, etc). It is longer and not as big of a diameter, if I remember right.

And it is a major pain in the a$$ to change if your engine compartment is tight. A 10mm racheting wrench will save you a ton of time and possibly some bruises to your forearm and shoulder....

The center bore, where the pump shaft goes, on the 496 impeller has two flats. The standard Bravo impeller has only one flat... "D" shaped.

Also, the pump housings are brass... most of the time, the whole pump is junk. Putting an impeller in a badly scored housing is an excercise in futility.