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Old 01-02-2015, 09:26   #1
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Next question: best 6-8kw generator for use several hours daily?

So far, you guys have helped point me towards having half a clue, so many thanks!

So yeah, 6-8kw for continuous use: recommendations greatly appreciated

(240v AC, 50Hz)

Northern Lights seem to be the big favourite, but out of our league in price terms, sadly!
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Old 01-02-2015, 09:46   #2
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Re: Next question: best 6-8kw generator for use several hours daily?

I have used Northern Lights on a boat for 9 years, and Onan on a boat for 18 years. Both have done well. The biggest maintenance item is the raw water pumps. They are Sherwood pumps of the Onan's and I don't remeber who made the pumps for the Northern Lights.
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Old 01-02-2015, 10:27   #3
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All the heavy-duty low speed gensets are good -- Northern Lights, Onan/Cummins, Kohler, etc. they all have 3 cylinders and run at 1500 rpm, and will last a lifetime. - they are rated for prime duty(continuous duty, as opposed to stand-by). Northern Lights is the best (by reputation), but they're all good. Sadly, they are all similarly heavy, and similarly priced.
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Old 01-02-2015, 10:39   #4
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Re: Next question: best 6-8kw generator for use several hours daily?

Heavy's ok, hopefully the Canal & River Trust will let us keep it on the ground, so long as it's not on the towpath!

Pricewise, if they really do run forever, would you recommend going second hand? And if so, what maximum age?

Thanks again!
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Old 01-02-2015, 10:48   #5
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Re: Next question: best 6-8kw generator for use several hours daily?

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All the heavy-duty low speed gensets are good -- Northern Lights, Onan/Cummins, Kohler, etc. they all have 3 cylinders and run at 1500 rpm, and will last a lifetime. - they are rated for prime duty(continuous duty, as opposed to stand-by). Northern Lights is the best (by reputation), but they're all good. Sadly, they are all similarly heavy, and similarly priced.

I knew that wasn't my "final question!"

As well as maximum still-reliable age, what should we watch out for if we buy second hand? Muchos thankyous!
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Old 01-02-2015, 10:56   #6
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Re: Next question: best 6-8kw generator for use several hours daily?

I have a 5kw Northern Lights and have 2960 hours on it since installed in 2003. When we leave the dock, we start the generator and turn it off when we return to a dock and plug in. Our longest continuous run was 99 hours last spring returning up the Tenn-Tom from Mobile to Demopolis. There was high water and heavy current and many times we were making 3 knots SOG. Next month we will start our 13th season with it and it has been extremely reliable. We commonly run it for 30 to 40 hours at a time.

I've had new injectors, valves adjusted, put on a couple of belts and changed impellers, oil and anti-freeze. No failures of any kind. I average .25 gallons per hour and 6 gallons in 24 hours. We run HVAC all the time and operate underway as if we were at the dock for power needs. The other 1500 RPM, 3 cylinder gensets most likely are comparable, but I can attest that the Northern Lights is worth the money. I would be wary of the faster RPM and single cylinder gensets that cost less. My experience on charter boats with that type is that they are noisy and unreliable.

I had to have a custom sound enclosure made for it due to the space available in lazzarette where it is mounted.


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Old 01-02-2015, 11:35   #7
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Re: Next question: best 6-8kw generator for use several hours daily?

Thanks, very helpful!
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Old 01-02-2015, 11:38   #8
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Re: Next question: best 6-8kw generator for use several hours daily?

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I knew that wasn't my "final question!"

As well as maximum still-reliable age, what should we watch out for if we buy second hand? Muchos thankyous!
They last for a long time taken care of and not run without a load.

The number one problem is bore polishing -- happens frequently when people buy them for air-conditioned boats and run them all night with the A/C mostly cycled off. Would be rare in the UK. You will need a pro mechanic to recognize these and other problems -- do a good inspection on potential finds.

Look for a unit with service records and proper maintenance -- just like buying a used car.

They typically last for 10,000 hours and more, but you should be able to find one with 1,000 or so -- just properly broken in.

There's probably not a maximum age, but obviously the newer the better -- easier to find parts, etc.
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Old 01-02-2015, 12:49   #9
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Re: Next question: best 6-8kw generator for use several hours daily?

Good stuff, thanks!
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Old 01-02-2015, 13:13   #10
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Re: Next question: best 6-8kw generator for use several hours daily?

Just one more thing -- don't be tempted to save money by buying a light weight one or two cylinder high speed standby rated genset. Especially not a one-lunger of any kind, but none of these will be really satisfactory for every day use. The difference in noise and vibration is incredible -- the three-cylinder low speed ones just make a pleasant murmer which does not interfere with life, whereas the high speed ones are very instrusive. The smaller Fischer-Panda generators have one cylinder roto-tiller engines which are run at redline in a sealed box -- not a recipe for a long life or for reliability.

The three-cylinder engines are industrial or tractor engines which are designed for 3000 rpm but are derated for low speed generator use. They are built for really heavy duty use on construction sites and in factories. The Northern Lights generators have the famous Lugger engines which are supposed to be the bee's knees. My Kohler has a 1,000cc three cylinder Yanmar which is also very sweet. It makes a pleasant mellow loping sound (three cylinder rhythm), very quiet, which does not interfere with life on board. You can't even tell that it's running from outside the boat.

Heavy duty gensets are much more expensive, but are one of the best investments you can make if you intend to use it daily. The light-duty ones are fine for occasional use -- maybe backup to a solar system, or for someone whose boat is in a marina with shore power, and doesn't anchor out that much. But for daily use, they are not satisfactory, in my opinion.
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Old 01-02-2015, 13:39   #11
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Re: Next question: best 6-8kw generator for use several hours daily?

Hmmm ok... Having done my homework with the gratefully received help from you guys, looks like our best option is just going to be some good maintenance on our existing engine, soundproofing the bejeezus out of the cavity, and investing in as much battery space as we possibly can! Well, I guess that was a bit of a wild-goose-chase, sorry lol! Thanks again for all your help
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Old 01-02-2015, 14:00   #12
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Re: Next question: best 6-8kw generator for use several hours daily?

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Hmmm ok... Having done my homework with the gratefully received help from you guys, looks like our best option is just going to be some good maintenance on our existing engine, soundproofing the bejeezus out of the cavity, and investing in as much battery space as we possibly can! Well, I guess that was a bit of a wild-goose-chase, sorry lol! Thanks again for all your help
That's all right -- you never know until you ask.

A decent way to make a lot of electrical power is with a heavy-duty school bus alternator on the main engine. An order of magnitude cheaper than the genset, and makes charging with the main engine far more efficient.
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Old 01-02-2015, 15:26   #13
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Re: Next question: best 6-8kw generator for use several hours daily?

Ahaaa! You just answered what I was going to ask next, cheers!
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Old 01-02-2015, 15:31   #14
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Re: Next question: best 6-8kw generator for use several hours daily?

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Ahaaa! You just answered what I was going to ask next, cheers!
Normal alternators are not designed for the production of bulk power, and are singularly ill suited to the purpose.

Buy a Leece-Neville school bus alternator (or Prestolite, or Balmar), with some form of external regulation (I use Adverc), and you will be very happy you did.

You will need to have brackets made, and a double-belt pulley -- a bit of a PITA, but really worth it. My alternator will crank out 2.5kW all day long without breaking a sweat; I can even run my washing machine with it!
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Old 01-02-2015, 16:55   #15
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Re: Next question: best 6-8kw generator for use several hours daily?

We've got experience with Northern Lights and with Kohler. For larger generators we'd go to Northern Lights. However, we have a Kohler generator in the size range you're talking about and have been extremely pleased with it.
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