I took apart the port side heat exchanger last night. Nothing in it. Completely open. Using the garden hose I flushed all the hoses thru & still nothing. I would think it has something to do with the pump. I am starting to wonder if I didn't have the belts on tight enough to spin the new stiff impellers. I basicaly tightened the belts to match how I found them. Possibly the pump pully was slipping. The belts looked like they need replacing. A little on the dried out side from sitting. New belts on the way as well & R&R kits on the way.

My 496 does not pull water unless I give the throttle a blip on start up. Just enough to stop it cavitating and get water circulating then its fine. These water pumps are apparently prone to this from picking up debris and scoring the back plate.

It is my plan to overhaul the pump in time but this has worked fine for me in the meantime, it circulates strong once it gets going.

You also may need to look for a collapsed hose at the transom assembly, at least run the hose on the drive and pull the feed hose that comes from the transom and see how much flow you get. I just did mine and one of the hoses was squeezed down about 1/2 by corrosion between it and the housing.

This may be dumb to ask!!!! But I will ask anyhow...On my pumps it is possible to have the hoses backwards...I do not think that you said what power you had..I have a friend that when through his carb 500s and forgot where the inlet and out let went..He asked a mechanic that worked at one of the larger marinas in A-Bay how to hook them up and he told him wrong...Just a thought

I currently have the front of the pumps of leaving the back plates attached to the hoses. If I take & put ear muffs on the drive & flow water thru it should the water be coming out of the top or bottom hose conected to the pump? I think this will tell me if my inlet hose is ok. I have 496 ho's.

Hope some one steps in here..I only am up on the pumps on my efi500..On the back it gives a arrow for the direction that it turns and lets you know where the inlet and outlet would be

Looking at the diagrams on mercruiserparts.com it looks like the inlet is the lower hose, so water should flow forcibly from there.

That's what I thought. Thanks for the reply. Tore into it a little more last night. Still no blockage found. Just waiting for the pump rebuild kits to arrive. I'm realy starting to think that is the issue. There are some pretty deep grooves in the brass.

Took the boat for a spin last night. Everything worked perfect after new belts & the R&R rebuild kits. Thanks for all the help/sugestions. Just in time for the long weekend.

Gotta love those R&R kits. I can't believe they don't make more of an attempt to market them.