MikeP
Legendary Member
- Joined
- Apr 12, 2005
- Messages
- 8,674
- Status
- OTHER
- Hatteras Model
- Not Currently A Hatteras Owner
I replaced the leaking seals (and bearings) on my M844K NL Genny's seawater pump. When I disassembled it I paid no real attention to the configuration because I have the NL service manual for the genny which includes the parts diagram for the pump. I started reassembling it as per the diagram but quickly realized that if I assembled it IAW with diagram, the seals cannot function.
The diagram shows the forward bearing, seal, washer, and snap ring in the wrong order . It clearly shows the assembly from rear (the drive gear end) to front (impeller end) being: front bearing, seal, snap ring, flat washer. This places a washer against the sealing surface of the front seal, mounted in the pump body, providing NO sealing surface at all between the impeller section of the pump and the forward bearing. It leaves the rear seal free to move around at random back and forth over about 1/2" of shaft with nothing whatsoever to bear against.
The order from rear to front in order to function must be: front bearing, snap ring, washer, seal.
The error is on page 3-6 of book P844K published by NL in 06/98. The pump is a Jabsco pump so whether the error is an original Jabsco diagram error or a NL error, I cannot say. If you have one of these books, the diagram shows the order (going forward) to be parts 7, 8, 13, 14. But to function, it has to be 7, 13, 14, 8. It may be that the Jabsco diagram for this pump (or others of the same general type could have the same error.
So if you are rebuilding such a pump, be aware that the info for doing it may be incorrect.
The diagram shows the forward bearing, seal, washer, and snap ring in the wrong order . It clearly shows the assembly from rear (the drive gear end) to front (impeller end) being: front bearing, seal, snap ring, flat washer. This places a washer against the sealing surface of the front seal, mounted in the pump body, providing NO sealing surface at all between the impeller section of the pump and the forward bearing. It leaves the rear seal free to move around at random back and forth over about 1/2" of shaft with nothing whatsoever to bear against.
The order from rear to front in order to function must be: front bearing, snap ring, washer, seal.
The error is on page 3-6 of book P844K published by NL in 06/98. The pump is a Jabsco pump so whether the error is an original Jabsco diagram error or a NL error, I cannot say. If you have one of these books, the diagram shows the order (going forward) to be parts 7, 8, 13, 14. But to function, it has to be 7, 13, 14, 8. It may be that the Jabsco diagram for this pump (or others of the same general type could have the same error.
So if you are rebuilding such a pump, be aware that the info for doing it may be incorrect.
Let me futz around here for a while and I'll post a pic.
