[WHOOSH]

R:

Check your thru-hull, from the outside. Does it have a grill that''s perhaps fouled with growth or a baggie (more likely) which flaps back & forth when the boat is underway, sometimes blocking the intake?

If hopping in the water with a mask isn''t an option for you, pull the hose off the thru-hull and then open the valve. Be prepared to stick something thru the thru-hull to temporarily clear it until you can get at it from the outside.

Have you pulled off the raw water pump (not just the impellar) and checked the face plate (too much wear for the impellar to be efficient) and keyway? Could it be slipping?

I think checking the heat exchanger is still a good idea. And now that we know it''s an issue or raw water flow, you need to check all the hoses in sequence, too. A pressure test won''t show a partial blockage.

Good luck. Just keep muttering ''this is boating; this is fun''. <g>

Jack