A friend was behind me, noted one of my motors was not spitting any water through the exhaust.....motor never over heated according to the gages. Then i was pulling it out, stuck my head back there and it was flowing water ......so i figured it was a weak impeller - switched it out, put it in the water - now it isnt even spitting water at all. We pulled it out - put it on a hose through the fresh water flush.....and it was fine (figured it would be). Put it back in the water - nothing. Just took the pump back off - impeller looks good......

Any thoughts????

Motors are 496 HO.....

I've heard the hose from the transom to the pump can collapse with age and restrict the flow. Maybe try running off earmuffs to see if you still get water.

Funny, I just pulled both my seawater pumps this weekend. I did overheat one engine the last time out. Well, it actually only got up to 200 degrees before it went into guardian mode. Since I didn't know the history of the impellers, I figured one must have gone bad. But, upon inspection, it was in great shape. I decided to replace both impellers, anyway. The problem turned out to be a bad thermostat. Note to self, check the easiest thing first!

Your fresh water flush system might have a plunger in the "T" from the hose attachment to the intake hose before the SWP. That plunger pushes down with the water hose pressure and stops water from coming in from the drive.

IF you have this plunger system, they can become clogged with sand and gook. This sounds like your issue.

Dan - I motor never went above 175......actually everything seemed normal. But when i pulled the boat out, I could tell something was wrong cause my brand new exhaust tips on the strbd motor were not nice and shiny like the port side.......

I will remove the "T" and see what i find.......that would be nice and easy.....

I inspected all the hoses, they appear to be fine.......

After i look at the "T" i was going to swap sea pumps, as the port side is functioning fine - this way i could eliminate one variable..........thoughts??

Better make sure you didn't burn up your exhaust hoses, too.

They looked ok.....perhaps i will remove one and check out the inside........

Did you get this figured out?

I swithced sea pumps, still same issue, checked the oil cooler, it was clean. I am pulling the drive back off since everything was fine until i serviced the drive.......

Just something to note, when I hook mine to the freshwater flush and turn the water on before starting the engine, it will backflush out thru the drives. Something you can check quickly without starting the engines.

Well, all figured out..........I should have kept the thinking simple at first.
It ended up being the gasket on the fresh water flush! Doubled up he gasket, and problem solved. Here I am taking sea pumps off, oil coolers, etc...........lesson learned!
Thanks to all for your input though.