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Old 04-27-2022, 10:55 PM   #1
PNM
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Northern Lights M753G-N8 Wet Exhaust Failure

My cast iron wet exhaust fell apart from rust. It shows 400 hours over 40 years. The boat has been on the hard for 8 years. I relaunched in September, 2021.

I removed manifold/expansion tank and found lots of black diesel residue in the #3 exhaust port. I found even more hardened diesel residue filling up the exhaust manifold exit port where it enters the failed failed wet exhaust.

I feared moisture had got into #3 but I turned the engine by hand and detected good compression followed by relatively easy turning motion between compression.

I shorted the contacts on the starter solenoid for an instant and the engine turned aggressively.

The next time I shorted the contacts the starter spun as if the bendix did not engage.

I think my expansion tank is solid - though I will test it before reinstalling.

I've cleaned out the hardened diesel residue from the engine exhaust port and the exhaust manifold/expansion tank. I will install a new SS wet exhaust elbow.

But, I have a question and would appreciate your thoughts. Did I break something when I engaged the starter for an instance? Bendix? Starter? engine?

I'll probably pull the starter and take a look, but I don't know how many times I have bumped a starter by shorting the solenoid without any negative consequences, so I wanted your wisdom before I proceed.

Have a great day.
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Old 04-28-2022, 07:33 AM   #2
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The exhaust elbows have a finite life, and I'd say 40 years is pretty good. The SS version is a good upgrade, but you still need to keep an eye on them. A lot of light load operation causes the soot accumulation that you are seeing. Run at heavier loads, or every couple of years pull the elbow and clean it out. I suspect the engine is just fine. Not sure about the starter. Maybe it's stuck from disuse? A little cleaning and I'll bet it's just fine too.
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Old 04-28-2022, 05:58 PM   #3
PNM
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Thanks for your wisdom.

I plan to order the parts after a short trip.

They are all in stock and I don't want them setting on the porch.

Then I will install a new battery and a new fuel filter, change the oil, then start it up.

My reluctance to move forward without some expert advice was due to the cost of a rebuild. Maybe I would not spend $500 fixing the elbow only to learn the generator is scrap.

Then I looked at the engine hours and the cost of a USED replacement NL generator and decided I would definitely rebuild it if it were damaged.

Nuff said! I will hope for the best and attack the worst if it happens.

Thanks again for you thoughts.

Have a good day.
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