Genset Water Overflow

I just finished changing all the older raw water hoses and impeller on my Northern Lights 673L generator. When I started it up everything seemed fine until water started flowing out of the overflow plastic container. I checked the fittings to the forward end cap(#32) of the head exchanger tube(#29) and put everything back together but water continues to come out of the overflow tube(#20). It seems like the raw water is mixing with the closed cooling water as there is no pink coolent left anywhere. I’m thinking since I only removed the forward end cap of the exchanger, the problem would be there and not somewhere else. Is there a trick to installing the end cap that I haven’t figured out? Cap looked and felt “newer”, but maybe their not sitting tight to the exchanger? Should I just remove and replace with brand new end caps? What am I missing?
Thanks in advance.

Possibly a hole has formed in the hx tube #29. Remove and pressure test #29.(maybe have it's professionally cleaned while you are at it.)

Did you change or mess with #32 in the parts drawing? It's non-obvious how to reassemble them (there are two of them, one on each end of the heat exchanger.


The wider part goes over the tank fitting, and the stepped down narrower part goes over the inner tube bundle. The two clamps secure the hose to each item, and isolates the coolant from the raw water side.


First you need to be sure the hose end is correctly over the two parts.


Second, you need to tighten the inner clamp first, then the outer clamp.


Since you got salt water in your cooling system, you will need to flush it and replace the coolant with new.

Since you have to take it apart again, take Aquabelle's advice first, followed by Twisted's.
Flush the whole "fresh" side of the system very very thoroughly ASAP, saltwater can really screw up a fresh/coolant water pump (don't ask me how I know this). Might be best to call in a pro and have them show you how it's done.

On the boots, the most fwd and aft clamp seals coolant from sea water. Clamps need to be placed correctly to get a good bite, and that can be hard to do as tube bundle is a bit short. And any crud on boot inside surface can prevent a seal. Rare for bundle itself to leak, but it is possible.

Ok, great tips, thank you. So I will try to re-seal the forward cap before undoing the rear cap, this was the only one I removed clamps from. Not sure of sequence on how I tightened them last time but it sounds like there is a preference on how to tighten each clamp. You are correct, not much there for clamping area. I swore it was all set after the second time and then a few days later leak started again. Maybe it slipped off?
The tubes actually looked very clean. Although old, the gen only has 350 hours on it. Will do a complete flush once solved, currently the boat is in brackish river water. I’ll try new end caps as a last resort before I make the dreaded phone call
Thanks again for the help.

So I finally made it to the boat and genset after 8-9 days, was laid up with pinched nerve and then flu. Sucks getting old. Took the front boot off and checked all interfaces, didn’t see anything odd. Reinstalled the front boot and clamps as suggested in posts and no overflow leaks. Will check again tomorrow for leakage between the two systems before I drain, flush, and refill the closed system. Will also order 2 new rubber boots to have on hand.
Thanks for all the pointers.

Also make sure that the ends of the heat exchanger tube are in good condition and not chipped at the edges. It makes them very hard to seal. Also don’t forget to make sure the holes in the outer tube are the right way up when you reassemble it. You will find that the back seal is the hardest to get right so just take it slowly.

Bums on a Boat

The poor guy on the Youtube channel "Bums on a Boat" had the same problem. It drove him a little crazy. He finally figured it out at about 8 minutes into this video after tearing every other thing apart.

Exactly my problem, that helps a lot. Funny thing is I think I have seen this video sometime ago, before I cleaned the engine exchanger.
Thanks