D2-40 VP Raw Water Problems

[pstadt]

I have two D2-40s driving saildrives on our cat. Engines have about 1K hrs on each. We ran for the last two days without incident but noticed very low output today from STBD raw water discharge in exhaust and visibly low flow through strainer and from impeller output into heat exchanger I suspected a worn impeller, so changed it with no improvement. (Old impeller was worn but no missing lobes). Also checked strainer for blockage and made sure it was primed before restarting. I had cleaned both hulls and all intakes a week ago. We've noticed over last several weeks that both engines are leaking raw water (perhaps a gallon after a day of motoring) from the impeller/block interface and am suspecting (after reading another thread that the shaft bearings and seals will have to be rebuilt).
Any ideas what would suddenly cause the lack of water on the STBD engine? I should have jumped over and checked to see if I had snagged a plastic bag, but we were sailing along single reefed at 9kts and were under a time crunch to get back home when I finished changing the impeller. Thanks!

[DougR]

Of course you could have snagged a plastic bag, or some other debris that partially blocked flow into the saildrive leg. You could remove the water hose going into the strainer and compare flow on one engine to the flow on the other engine. You also might try using the dockside water hose to back flush from the strainer down thru the saildrive.
As to the leaking seals,it might be seal wear, or it might be that you are experiencing some restriction on the pressure side of the system. Check for restriction in the HE element or corrosion build up in the exhaust mixing elbow.
DougR

[Acushla]

Any leakage on the suction side of the raw water pump between the pump and the water inlet point has a significant effect on cooling water flow. This can include the water pump shaft seals.
If the pump shaft is grooved at the seal path then this will also require replacement or refurbishment.
Hose connections on the suction side are always difficult to test for suction leaks but you need to ensure they are all leak free. I use a small air compressor off the 12v system to put the suction side under a small positive head and soapy water sprayed on all the joints to check for any bubbling/foaming.

Cheers
Acushla

[pstadt]

Thanks DougR and Acushia! Excellent advice that I will try out. i spent a little more time tonight with the problem (before seeing your posts) and observed that the seals are loose on the shaft (I could move each back into their position and noticed the spacer between the two is only about the size of an o-ring, doing nothing to hold them in place). I removed the outlet hose from the pump and with the sea valve closed on the sail drive, filled the hose with water - I could watch the level go down inside the hose and that water dripping out of the back side of the impeller housing/seal area. I think I'll buy a new pump and try to rebuild the existing one for the other side that is beginning to show the same dripping symptoms.
Thanks for your replies and thanks again for the good advice!

Pat