NL generator water pump issue

[Olly75]

My generator saga continues...

It's a NL 643, ran it yesterday for around an hour with no issues. This morning started her up and no raw water flow. Took the front plate off the water pump and the impeller is fine, so turned it over with the front plate off and the pump isn't spinning.

First question, if you turn the generator over without the pre heat switch pressed, should the water pump spin?

Second question, I replaced the water pump and it has been run for 15 hours since the change out (the previous one was leaking). Assumong I didnt get a bad water pump off the shelf (it came from a NL supplier so seems unlikely), what would be the next thing to check for diagnosis?

[coopec43]

Generators Northern Lights - remove raw water pump

boatdiesel.com › ... › Marine Generators › Generators:Northern Lights

Nov 17, 2018 - Also ran into this problem when a new impeller was just a tiny bit shorter than ... 4, Generators:Northern Lights, Affordable parts source for M643 raw water pump ... If your boat is in salt water and you´re going to leave your NL genset for weeks ...raw water pump leaking

17 Nov 2018
rebuild raw water pump
19 Jun 2016
raw water pump shaft seals
11 Nov 2018
fresh water cooling system
16 Nov 2018

OPERATOR'S MANUAL
https://www.northern-lights.com/medi..._pdfs/O101.pdf

[tkeithlu]

In response to your first question, the water pump is geared to the engine, being vital, and should turn if the engine turns.

The first question for you then is does the shaft to the impeller turn when you turn the engine? If it doesn't, then pull off the pump, and see if you have stripped the linkage between the engine and the pump. If it does turn, then the impeller is not attached, so look under it. Also check that the impeller itaself is not torn loose from its bronze core. I don't think that this is going to turn out to be a complicated problem. The fact that you recently replaced the pump suggests a problem in one of those three places.

[Chotu]

Did you look REALLY closely to see if the shaft was spinning but the impeller wasn’t?

Most of those NL impellers look all black on the front but you can remove the part over the shaft to have a view of it. Try spinning it again and see if the shaft spins, but impeller doesn’t.

The odds are it’s the impeller.

Or... just stick a new impeller on and try again.

This should be a really really small issue. I know you’re at your wit’s end with that generator but once you get all these issues worked out, it’s going to be the most reliable generator you can possibly imagine.

[Olly75]

Thank you for the responses.

So I pulled the impeller which was fine, bumped the engine and the shaft didnt spin, took off the water pump and, drum roll, the nut on the end of the pump shaft had worked loose allowing the gear to spin freely......

I'll tighten it back up and give her a spin...

[Olly75]

Thank you for the responses.

So I pulled the impeller which was fine, bumped the engine and the shaft didnt spin, took off the water pump and, drum roll, the nut on the end of the pump shaft had worked loose allowing the gear to spin freely......

I'll tighten it back up and give her a spin...

[tkeithlu]

Hurrah! Let's hear it for mechanical diagnosis!

Damned glad to hear that you found it, and that it was not a major failure deep in your engine.

[s/v Jedi]

Don't forget the thread locker.

[SUKHA]

Originally Posted by Olly75

Thank you for the responses.

So I pulled the impeller which was fine, bumped the engine and the shaft didnt spin, took off the water pump and, drum roll, the nut on the end of the pump shaft had worked loose allowing the gear to spin freely......

I'll tighten it back up and give her a spin...

I had the same issue tightened her back up with a little threadlock and working great again. Thanks to this thread.