Water Pumping Issue
 

We have a 32 Fountain with twin 6.2 MPX engines and raw water cooling system, new impeller kit installed after customer came in and said it was running hot. We flushed the entire system and found minimal restrictions, all were cleared. Now it will not pick up the water on it's own. When the flush is installed at maximum pressure and the low water pickups taped off, it will not pick up the water. We removed the drive and checked there for restrictions, none found, but flushed anyhow. With a special tool we made to fit directly into the water pickup tube in the transom assy, we can apply water pressure from the hose and the engine will pump and circulate water, but it will not pick it up on it's own. WTF, please anyone have any ideas, would surely appreciate them.

Is there a check ball system installed?

Yes but it is on the recieving side of the water flow, not the intake, could this be causing the problem of why it is not taking the water up on it's own? Seems that wouldn't have any effect on the intake side, but I am looking for answers here!!

Those spring loaded check ball systems/gadgets are JUNK! Hollow it out if you can. They get all gummed up with sand and other crap, even if you have a strainer.

Also, are you sure you have the hoses in on the right ends of the pump?

Yes, they are right. Also when I run the hose even at a low pressure directly into the water intake tube at the transom assy, it will pump the water, you can see it surging the water flow. It acts as if it just doesn't have enough suction, but there are no visible signs showing a leak, could the whole damn pump be bad in some way? I installed a new o-ring seal that came with the new Mercury impeller kit.

are you sure the pump is turned correct, i did that one time a bought three diff housings and finally figured i clocked it where it was sucking from the discharge side,

If there is a freshwater flush system check that out where the tee is it has a checkvalve in it that could be stuck

I had one like that once. Tried everything, and like you, I couldn't find any wear in it. Swapped it to the other motor, still wouldn't work.

Finally I got frustrated and went and bought a new housing, put it on, and poof, it worked like a charm.

Tossed the old one in the trash and never looked back. :)

Installed the "special" flushing kits from Perko, all worked well for 2 years. Then after boat sat for 4 weeks on the lift, the little check valve stuck closed on the suction side and I smoked two Impeller/pump kits before figuring it out that it just would not open and why it would run fine on the flushing hose but not pick up water from the pickup. Removed both kits and took out the sliding plunger valve with malignant violence and reinstalled. No problems in 6 years.

The piston plunger had a rubber type face and it was glued closed by buildup of slime on the face, it was only couple of thousands thick, but glued the valve closed as if I had pumped superglue through there.

Thanks to each and everyone of you guy's I loved your comments and thoughts on this crazy and frustrating issue I have been having. There are no flushing devices on these motors, they are just totally stock 6.2 MPX MerCruisers and have the factory cooling systems on both, no strainers, nothing. Wish it could be that, but I have boiled it down to what the gentleman with the Cigarette Cafe' Racer said, the actual pump unit itself is bad, must have seals leaking or something, so a new one is going on it. I am so glad on my personal boat I bought and rebuilt back to factory specs a 1999 Mercury Racing HP 500 carb engine. I love this set up, only modification I did to it was rather than a circulating pump, I installed a crossover, I have plenty of water flow. And I replaced the Crane springs with an Isky set thats stronger, it runs great. Thanks again everyone, I really appreciate your input.
:thankyouthankyou:

I had a similar issue after installing a new impeller in my 496 sea pump with about 300 hours on it. What happens is the well documented problem of the impeller wearing grooves in the body and cap of the pump (on the ends of the impeller). When you install a new impeller it does not seal in these grooves. The old one did as that is what wore the grooves in the first place and that is why you did not notice a problem until after the impeller change. The new impeller thus leaks around the ends of the impeller between the impeller and body. This is generally not much of a problem unless there is air in the system like when running on a hose. The pump will not self prime in this condition due to the internal leak. If you can get water into the pump it will work fine (as you found out). Fortunately this means the pump will generally perform to an adequate level in normal service. Running off muffs on the hose is an entirely different matter however. The only solution is to replace the pump with a new one or the one made by Hardin Marine or to rebuild the old pump with the kit made by JC Marine that retrofits replaceable end wear plates.

Dan