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Old 06-14-2014, 07:18 PM   #21
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I recently yanked my Northern Lights M-643 4.5KW genset and reconditioned it at a local Generator shop. I was surprised how few Northern Lights units there were in the shop. According to them, Kohler, Onan, and other lesser makes keep them in business. When I yanked the back end off my old 4.5, it was truly a work of art compared to the other windings I saw in the shop. I had considered buying a newer genset, but after being exposed to that, I rebuilt the Northern Lights unit instead. $3500, but.....
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Old 06-14-2014, 07:54 PM   #22
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does Northern Lights make their own generator ends or are they outsourced and the same on other gensets?
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Old 06-14-2014, 08:36 PM   #23
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does Northern Lights make their own generator ends or are they outsourced and the same on other gensets?
Northern Lights used to use a Japanese generator end for their <10K units. IK do not remember the brand name.

They have switched to exclusively Marathon generator ends.
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Old 06-14-2014, 09:18 PM   #24
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Truck engines don't run a the same RPM hour after hour no matter the load on them. Plus they have a transmission attached to them. It's apples to oranges.

Light loading a Genset prime mover does cause glazing of the cylinder walls and other issue that shorten the time between rebuilds.

Now if the Genset is in a pleasure boat that is only used a couple of hundred hours a year, the difference that light loading can make in the times between rebuilds may not be of much concern.
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Old 06-14-2014, 09:31 PM   #25
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Truck engines don't run a the same RPM hour after hour no matter the load on them. Plus they have a transmission attached to them. It's apples to oranges.

Light loading a Genset prime mover does cause glazing of the cylinder walls and other issue that shorten the time between rebuilds.

Now if the Genset is in a pleasure boat that is only used a couple of hundred hours a year, the difference that light loading can make in the times between rebuilds may not be of much concern.
Bill

You need to remember that a recreational marine generator has varying loads put to it. It will run at a very high output for periods of time, and then a lower output during other times.

The only actual cylinder glazing I've seen has been a very lightly loaded very old design genset that was powering a microwave site. That unit had a constant very low load. Certainly not what you see in a generator in a recreational boat.

And, as you indicated people in recreational boats will never see the long run times that we see in prime power applications, so engine size is for all practical purposes irrelevant to engine life in this application.
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Old 06-14-2014, 09:36 PM   #26
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Bill

You need to remember that a recreational marine generator has varying loads put to it. It will run at a very high output for periods of time, and then a lower output during other times.

The only actual cylinder glazing I've seen has been a very lightly loaded very old design genset that was powering a microwave site. That unit had a constant very low load. Certainly not what you see in a generator in a recreational boat.

And, as you indicated people in recreational boats will never see the long run times that we see in prime power applications, so engine size is for all practical purposes irrelevant to engine life in this application.
Plus ....many boatowners know not to leave it too lightly loaded for too long and take steps to load it up somewhat.

Hopefully they are smart enough if all they ever do is load it up with extras...then maybe a smaller one in the future would be appropriate.

But not having enough genset when you want it (or shore power for that matter) is a pain to load shed....and like you said, the generator side which can be awfully expensive to replace also.....
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Old 06-14-2014, 09:50 PM   #27
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Kevin:

You are no doubt right about generator ends. Bigger is certainly better. No question.

But consider this for the engine. A bigger is better philosophy will select a 7-12 KW unit to run all of the possible loads at once. But at night when the genset is only running a 16,000 btu load at about 15 amps, it is running at zero load probably 70-90% of the night time and 20% load for the rest.

So for maybe 7-8 hours that genset engine is doing nothing more than pumping air through the engine. There is no load on it because at night the A/C cycle time is low. The cylinders cool down, combustion is compromised, and cylinders glaze.

I remember the lecture I got years ago from the head of Bayshore Marine in Annapolis after they installed my 5 KW Northern Lights genset. The guy told me that he does a good business rebuilding gensets that spend their life running 24/7 in the Caribbean, mostly running A/Cs. They come back to Annapolis and they are burning oil, hard to start, etc.

He pulls them out and removes the head and pistons and runs a hone down the cylinders to remove the glaze. Buttons them up and they are good for another season of light load abuse.

Generator engines are unique in terms of running at low load relative to propulsion engines. They run for long periods overnight at NO LOAD. That is bad, bad, bad for them.

So it is all a compromise like almost everything in boating, between loading the engine enough and not overloading the generator end when you need the output.

David
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Old 06-14-2014, 09:58 PM   #28
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Because of the engine issues being arguable at best, and the generator end issues favoring a larger generator, and the inherent frequency stability of a larger generator set, I'd recommend on the larger generator given a choice. .
Kevin does this stuff for a living and knowing him personally makes my vote . A caveat though, the genset is only as good as its associated systems and installation.
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Old 06-14-2014, 10:55 PM   #29
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Kevin:

You are no doubt right about generator ends. Bigger is certainly better. No question.

But consider this for the engine. A bigger is better philosophy will select a 7-12 KW unit to run all of the possible loads at once. But at night when the genset is only running a 16,000 btu load at about 15 amps, it is running at zero load probably 70-90% of the night time and 20% load for the rest.

So for maybe 7-8 hours that genset engine is doing nothing more than pumping air through the engine. There is no load on it because at night the A/C cycle time is low. The cylinders cool down, combustion is compromised, and cylinders glaze.


Generator engines are unique in terms of running at low load relative to propulsion engines. They run for long periods overnight at NO LOAD. That is bad, bad, bad for them.

So it is all a compromise like almost everything in boating, between loading the engine enough and not overloading the generator end when you need the output.

David
David

There is a huge difference between my engine loading thoughts and the one you described.

I am/was thinking of a scenario of varying loads with a low of somewhere in the 10% range and a high nearing full load.

You are describing loads between 0 and 15% (of a 12KW generator) with the predominant load being zero and a 10-30% duty cycle of any load at all.

I agree that is bad juju.

In the scenario you described I'd recommend...

A large capacity inverter/charger.
A decent sized house bank
A auto start controller on the generator that will start the generator when the house bank reaches 50% and turn it off when the house bank reaches 90%

In that scenario you'll save lots of fuel by running the generator only part of the time, and you'll avoid running the generator with no load.

I would still size the generator to run all the loads on the boat, which with only one AC system at 15 amps would work just fine with probably a 8 or 9 kw generator. (depending on other loads)

Then when the generator turns on the initial load will be around 25 amps for the charger, plus 10 amps for the hot water heater which would be a 50-60% loading. Over time the generator loads would drop lower, then the generator would turn off for a period of time, then repeat the cycle. Assuming an electric stove/oven and you could come close to maxing out the generator when running the stove, and worst case scenario for other loads.
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Old 06-14-2014, 11:10 PM   #30
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Kevin does this stuff for a living and knowing him personally makes my vote . A caveat though, the genset is only as good as its associated systems and installation.
Thanks Tom!
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Old 06-14-2014, 11:28 PM   #31
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At the risk of derailing an interesting thread. What would be needed to permanently install one of the portable Honda inverters on a boat?
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Old 06-14-2014, 11:47 PM   #32
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At the risk of derailing an interesting thread. What would be needed to permanently install one of the portable Honda inverters on a boat?
On one of our boats

We put hold down straps on the swim deck and a power inlet near by.

That isn't permanent but its as closes as I think you can get safely.
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Old 06-15-2014, 12:58 AM   #33
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That's an interesting idea Kevin, elegantly simple too.
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