Raw Water Pump Rebuild

I’ve got a Northern Lights M643 5kw generator. After running last night, I noticed some water in the drip pan. It appears my raw water pump is leaking around the shaft. Since it hasn’t run for a while, is this something that will fix itself with continued running?

If not, I see the rebuild kit is available from Diesel Parts Direct (great service and super quick shipping, by the way) but I’ve never done one of these before.

As I’m sure many here have probably done something similar, I’m looking for any tips or pointers. Any special tools needed?

Removal and installation looks pretty straightforward, but is there anything I’m missing?

Also, is there any better place to get the parts?

Thanks!

I have the same pumps on a two Northern Lights gen sets. The ceramic seal requires careful installation. You need to have a tool that will slip over the shaft that is larger in diameter than the seal. The end surface of the tool needs to be flat. Carefully drive the seal into the housing with light hammer taps to the tool end. The seal will then be flush with the back of the housing. The kit will have new bearings and seals for the engine side also -- It took me about 30 minutes per pump to rebuild once I made the tools. Make sure you install all the bits and pieces in the correct order.

Diesel Parts Direct is the best source that I have found for the parts. Removing and installing the bearings and seals is best done with a small press. Using a hammer is possible but tricky to do without damaging something. A large vice can serve as a press but an actual shop press makes it much, much easier.

My advice is buy a new pump to replace the old one. Then rebuild your old one and use it for a spare, which you will eventually need. Bearings last a long time and likely won’t need replaced unless the pump has really got a lot of hours on it. It will need new seals, wear plate and impeller. Buying the whole rebuild kit is one way to do it but more expensive than getting only the parts you need. You could buy the rebuild kit the first time, use the needed parts for the rebuild, and keep the rest for future repairs. Order replacements for the seals and/or other parts you needed from the kit and you will have the full kit for next time.

Over time the pumps will eventually leak so its nice to have 2 in rotation so you can always swap it out and do the rebuild when it is convenient.

A leaking shaft is a warning sign that the seal(s) are about to fail which could result in sea water mixing with the engine oil. The cost of repairing this scenario is enormous.

Over the years, I've tried repairing pumps myself (not very successful) and then professionally (parts plus time). Now, with the price of pumps having dropped so much (I use Sherwood on my Cummins engines) it's just not cost effective to do anything but replace with a new pump.

Hence, I carry replacement pumps for the two Cummins and two generators. Interestingly, since I stopped repairing pumps, the time between failures has increased significantly! Success.

I've been rebuilding my pumps, raw and coolant since the 60s. For pressing bearings, etc., Harbor Freight sells an arbor press that's better than trying to hammer parts in place. I buy my bearings and seals online and only buy a kit if there's some damaged parts. If I only need bearings and a seal it costs less than $20 to rebuild any pump I have, currently Detroit, Onan or Perkins.

There are probably several videos on Youtube on rebuilding a pump similar to yours.

Hi, a little next to topic,

Does anyone know who is the manufacturer of Northern Lights M643 5kw Generator basic diesel engine?

I suspect it was Kubota and NL marinated it? I have the same generator, but difficult / expensive to spare parts on this side of the world.

My NL 753G's engine is made by Shibaura according to the plate mounted on the engine.

The NL 643 is a Shibaura 643.

DEPCO pump in Clearwater can do the rebuild. Those ceramic seals are picky and in my experience are best if run often.

bayview said:

DEPCO pump in Clearwater can do the rebuild. Those ceramic seals are picky and in my experience are best if run often.

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I agree. Call DEPCO and get a new pump instead trying to rebuild this old one. They are very friendly and helpful.

I had to do the same with my Onan. PITA changing it out.


Depco Pump Company