Originally Posted by flawler
The pump pictured was NOT my pump and that post was not my post. I am talking about the raw water/seawater pump. The original thread had a video of a running engine pulling water out of a bucket; my reference was to that video.
My raw water circuit acts as if the impeller is not there, even though I put in at least two different ones called for by the part numbers in the manual and primed it thoroughly after screwing it down tight.
I am looking for possible causes of the problem and possible solutions. Is the RAW WATER PUMP failing under load? Is there a leak in the system that I have missed? Has anyone else experienced a similar problem?
Thanks for any helpful suggestions.
Relating to your Raw Water Pump, can you tell us how and when the pump failed? Was it gradual with an accompanying rise in engine operating temperature, or was it suddenly?
1. Don't take this wrong, but did you put it back together correctly with the cam and endplate correctly installed and plenty of appropriate lubricant?
2. Are you sure of the impeller part number and size? I once fought the same problem only to find I had been given a replacement impeller that was not wide enough. It had too much side clearance against the housing and would not seal sufficiently to pump water. When I finally installed the proper impeller, it worked perfectly.
3. Another time, I had to make a new pump cover gasket for an emergency repair. The gasket material I first used was too thick and the pump would not prime. I cut another gasket out of a brown paper bag and it worked perfectly.
4. If the pump cover or housing are too badly scored or worn, the pump will not prime or pump properly.
5. If the shaft lip seal is damaged, the pump will not prime or pump properly.
I believe you mentioned that you tried the bucket test, but did you thoroughly check the water supply to the pump? Are the through-hull, seacock, hose and raw water strainer all clean and leak free. If not check these.
1. The exterior raw water strainer, if fitted, can be blocked by a plastic bag or other debris.
2. The seacock/valve can fail with the operating shaft breaking at the ball, allowing the handle to move, but not actuate the ball. I have one on my bookshelf that broke like this. The handle turns freely, but the ball is frozen in a slightly open position.
3. The seawater strainer cover gasket can become damaged and leak air which can cause the pump not to prime or to pump poorly.
4. Hoses have been known to delaminate on the inside in such a way that the liner comes loose and closes off the water flow on the inside.
5. Finally, are all of the hoses, adaptors and clamps tight and leak free? I have seen common brass hose adaptors used that deteriorated and became porous and leaked.
Other members may think of something I have forgotten, but this is all I can think of right now.
is a good source for Johnson pumps and parts.
Best of luck