Generator heat exchange failure?

[Islanddreamer]

Northern Lights M673M 5.5kW older generator but with <300 hours. As a routine maintenance last year had the HX removed, cleaned out, and put back in place. Winterized prior to HX cleaning. Not sure if it is original - have had the boat for a little more than a year. The way the gen was installed, I needed to have someone shorter, thinner, and more flexible than me get to the non-routine service side of the gen - hence having it done versus doing it myself. I can get easily to the other side of the engine.

Fired generator up and drip pan had diluted antifreeze in it. Vacuumed up the mess. Cleaned pan. All connections are tight and not leaking - no leaking hoses. Did the same routine, but this time the Admiral fired the gen up while I was in the bilge with the sound shield off. After about 3-5 seconds of running, a mix of water and antifreeze was coming out of the overflow tube - which I caught in an empty water bottle this time to avoid the cleanup. Thought it was odd that I didn't need to add a lot of antifreeze after HX was repaired.

Here is the question - if a tube in the HX fractures, the overboard water will enter the block and the only way out is the overflow tube - correct? Again - everything is tight except that when the gen runs, coolant / water streams from the overflow tube.

Advice?

mike

 

[twistedtree]

Do I understand that you just serviced the heat exchanger? I'm not sure about the 5kw, but the larger NL gens have a special boot that forms the seal/barrier between the sea water and coolant sides of the heat exchanger. There boot needs to be positioned correctly, and the two clamps need to be in the correct location, and tightened in the correct order to get a good seal.

That may be the only issue. But if it is, you will need to go a thorough coolant system flush and add all new coolant.

 

[Islanddreamer]

I replaced the boots as well because they had buildup, and they were reinstalled. As to correctly - I cannot say because it wasn't me - but someone I trust. When I'm done, I'll need to get Middle River out of the block!

 

[Ski in NC]

Some coolant will get expelled due to thermal expansion. Maybe a couple ounces from cold to warmed up. If boot leaks, sea water will mix with coolant and if you run it with cap off, the mix will come out continuously.

 

[Islanddreamer]

Do I understand that you just serviced the heat exchanger? I'm not sure about the 5kw, but the larger NL gens have a special boot that forms the seal/barrier between the sea water and coolant sides of the heat exchanger. There boot needs to be positioned correctly, and the two clamps need to be in the correct location, and tightened in the correct order to get a good seal.

That may be the only issue. But if it is, you will need to go a thorough coolant system flush and add all new coolant.

twisted tree- the boot was the problem. There is such a small margin for error it is amazing. You can't count on the old marks where the old one came off either. Thank you- you saved me considerable stress.

mike

 

[twistedtree]

Cool. Glad you got it fixed. I had to remove one of my boots to fish out some impeller blades, and had to fortune of NL's training guy coaching me. I likely would have screwed it up otherwise.

 

[Rebel112r]

I would bet, the exhaust elbow is plugged up and salt water pump is forcing sea water by the o rings in exchanger. I have the same gen, and had the same troubles when I bought the boat. Easy fix, replacement elbow is stainless, and not cast as is the original. 300 or 400 for new part if I am remembering correctly.

 

[Rebel112r]

Oops, didn't see last post.

 

[Islanddreamer]

OK so I have to re-ignite this post again. Problem came back. There is only one correct way to put the HX in, and after 3-4 removals, re installations, I need to go back and check the exhaust elbow.

Here is my question- the generator - although an older installation only has 198 hours on it overall. Is it possible for a generator with this low number of hours to have a plugged exhaust elbow?

Incidentally it has had a full five minutes of use this season to run my Keurig while away from the dock. Sheesh.

 

[twistedtree]

Here is my question- the generator - although an older installation only has 198 hours on it overall. Is it possible for a generator with this low number of hours to have a plugged exhaust elbow?

Yes, it is a distinct possibility.

 

[Rebel112r]

This is what I changed. I think the price has come down, to less than 300 bucks.

 

[Larry M]

...Here is my question- the generator - although an older installation only has 198 hours on it overall. Is it possible for a generator with this low number of hours to have a plugged exhaust elbow?...

Yes, it is a distinct possibility.

Yes. We had the same generator. The cast iron exhaust elbows on this model, in my opinion, is a major weak link. They are a maintenance item. We had one fail in less than 200 hours also. We changed to an after market stainless steel replacement and never regretted it.

 

[pacopico]

The number 1 cause of premature failure of a wet exhaust elbow due to "plugging" is lightly loading the genset.

Running for a few moments to make coffee and not loading it up is a no-no!

 

[Islanddreamer]

Yup- I have a diesel gen for the house too, and normally I run it with a ton of things operating.

We've really not used it that much at all as we are recreational boaters for now as I still work, but I don't want to have a system onboard that isn't properly functional. Thanks for the exhaust elbow help- later this week I'm going to pull it off. Latest price on this part isn't too bad either.

 

[fgomezpi]

My Northern Lights generator 673M does not stop sending water to the reservoir and the water in reservoir does not come back to the generator after cooling. I replaced the generator cup and removed most of water from generator but does not help. Any advice? Can this be a heat exchanger failure?

 

[jimdavi]

No expert here but I recall reading something about the heat exchanger end cap rubber boots not being on correctly can cause issues.