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Old 06-13-2014, 06:45 AM   #1
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Smile Which Generator?

I'm in the market for a 7-8KW generator...anyone got the map of the minefield?
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Old 06-13-2014, 08:03 AM   #2
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You can't go wrong with Northern Lights. And I've also had good luck with Kohlers and Westerbekes.

Properly maintained any of the major brands make for reliable units.
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Old 06-13-2014, 08:28 AM   #3
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If you're on a budget phasor will do, if not and you want the best as Bill said go Northern Lights.
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Old 06-13-2014, 08:39 AM   #4
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Looked into this last year when I thought I might have to replace my 8 kw Westerbeke. General opinion appeared to be that Northern Lights was the premier brand today and that Westerbeke was losing market share.

Also after quite a bit of thinking and analysis I concluded that for my needs on a Krogen 42 that the 6 kw or 7 kw was the proper size.
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Old 06-13-2014, 04:41 PM   #5
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MarkV: how did you determine you need 7-8kW? Are you replacing existing or have you worked out that is what you really need?
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Old 06-13-2014, 05:50 PM   #6
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Another brand to consider for value is NorPro. Good electrical end; primarily Yanmar engines; many happy users in the Hatteras community, no direct experience myself. At one point I was in the market for a second "night" generator of about this size and after a bunch of research and talking to folks, had it boiled down to NorPro or Onan (very quiet, lots of service outlets, other genset is an Onan). Since we were cruising extensively, having engines and gen-ends with good networks was important.
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Old 06-14-2014, 07:46 AM   #7
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I would only go with the Northern Lights. Also don't go too small, you rarely take
items off a boat.
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Old 06-14-2014, 09:49 AM   #8
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Another brand to consider for value is NorPro. Good electrical end; primarily Yanmar engines; many happy users in the Hatteras community, no direct experience myself. At one point I was in the market for a second "night" generator of about this size and after a bunch of research and talking to folks, had it boiled down to NorPro or Onan (very quiet, lots of service outlets, other genset is an Onan). Since we were cruising extensively, having engines and gen-ends with good networks was important.
You bring up some good points.

Norpro is what we generally refer to as a "packager", in that they put together generators from off the shelf components.

A generator is nothing more than a prime mover (engine) governed at a specific RPM coupled to a generator end.

You can evaluate a "generator" by examining its components.

1. Engine... This part is easy because there are only a few engines being used for small generators. Yanmar, Kubota, Isuzu are a few brands.

The engine is governed in RPM by the governor. Generally in small generators this is a factory supplied unit that is part of the injection pump. It can also be a bolt on electronic unit which provides better frequency regulation.

The challenge with marine generators isn't the engine, its the equipment used to marinize it. This comprises of generally a heat exchanger, possibly a liquid cooled exhaust manifold, seawater injection elbow, and seawater pump.

These cooling systems are what you are probably going to need parts for. This is where to be careful with generator companies. The cooling system probably has special hoses with specific bends, things like that. Sourcing these kind of parts when you need them might be problematic. Also remember that the reliability of these systems is often dependent on the engineering put into them. Small companies do not have real R&D departments. This can lead to reliability problems

2. Generator End... Generator ends are simple in theory. Spin it at its rated rpm and it makes power. The problem is that generator ends represent a huge part of the cost of a generator and packagers are always trying to find a less expensive generator end in order to stay competitive.

All generator ends make power, but if you look at the components you will find huge differences. Brand names to look for are Marathon, Stanford Newage, and to a lesser extent Leroy Sommer. Marathon is based out of the US, and parts are available world wide. Newage is based out of the UK, and I've found that parts are readily available. Leroy Somer is a Emerson company but they have a pretty small market share. I cant vouch for or against Leroy Somer parts wise.

Other brands of generator end of course exist, such as Syncro out of Italy and several China based manufacturers, but be careful of long term parts support.

As far as technology generator ends are regulated by one of several methods. The best is electronic voltage regulation. This is what all industrial generators use. Then there is transformer based regulation. This is an older technology. Not nearly as accurate as electronic, but very simple and reliable. (lots of Westerbeke generators use transformer regulation). Last is capacitor regulation. Stay away from this. The capacitors tend to go out making you scrounge for parts. Also and this goes without saying stay away from any generator end that uses brushes. As an industry we got away from brush type generator ends in the late 70's.

The lesson here that I hope to deliver is that while small packagers can save money and make a good product, you as the purchaser need to examine what you are buying, because quality varies. Also consider where you will find parts if your packager either discontinues support, or goes under. Remember that a generator is a 20 + year investment.
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Old 06-14-2014, 10:47 AM   #9
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My 8 KW Westerbeke has 6500 hours, in that time I've used 3 heatexchanger and 4 impeller. The Mitsubishi Motor on this Gen. is very good.
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Old 06-14-2014, 12:42 PM   #10
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Excellent write up by KSanders. I would add that Kohler is also a 'packager' and that the packager business model shouldn't be assumed to be inferior....as ksaunders says, just be conscious of parts availability.
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Old 06-14-2014, 12:57 PM   #11
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There are a few brands that are all pretty much equals...not sure how Northern Lights got such a great rep other than marketing ...good package but not sure head and shoulders above others.

As years go by...they all seem to experiment with suppliers...so make sure your "ends" are what you expect as Kevin S. posted.

The other issue is parts..make sure your cruising grounds have at least a few suppliers, servicing centers.

25 year old, 5400 hr low maintenance Westerbeke here...
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Old 06-14-2014, 02:35 PM   #12
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Ksanders, thanks for the write-up. I went and learned something today. Good stuff.
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Old 06-14-2014, 02:52 PM   #13
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Ksanders, thanks for the write-up. I went and learned something today. Good stuff.
Ditto. Though I'll probably not take advantage of it since I uninstalled the generator that came with my boat and switched to 1200ah of AGMs thru a 3kw inverter. I'd rather carefully control usage than install a replacement.
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Old 06-14-2014, 03:08 PM   #14
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Thanks guys!
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Old 06-14-2014, 03:47 PM   #15
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We haven't talked about size, much. One poster said buy big. I totally disagree.

You can add up all of the things you might want to run from your genset and that might tell you to go with a 12.5 KW unit. But I prefer to add up all of the things I HAVE to run simultaneously and size the genset for that capacity.

So what if I have to turn off the water heater for a few minutes to use the microwave or my wife's hair dryer.

A genset that is loaded well will last longer than one that is loaded lightly. That 12.5 KW unit that you run all night to operate a 16,000 btu A/C on a 20% duty cycle is just pumping a bunch of air 80% of the time. That isn't good for them.

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Old 06-14-2014, 03:59 PM   #16
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Our 8KW generator is to big for us. The replacement will be a 6KW. Running the water-maker, water heater and charging batteries is our standard at anchor and that's about 4.5KW. Even there, the water heater takes less than 1 hour and we don't make water every day.
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Old 06-14-2014, 04:36 PM   #17
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Kevin...

What's the deal with inverter type gensets like the little Hondas?

Someone asked awhile back and can't remember if you jumped in and explained why we don't see more versions of the type in permanently mounted sets.
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Old 06-14-2014, 06:00 PM   #18
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I think that the reason you don't see inverter type marine diesel generators is that the market is too small to justify the development work required. Honda has sold a million of their gasoline inverter gensets. The marine market is a tiny fraction of that.

You can do something similar manually with a DC genset driving a bank of batteries that supplies current to a big inverter which powers your AC loads. When the load gets light, you throttle down (or turn off) the genset.

But it wouldn't be the same as a Honda type inverter genset. Those operate at a more efficient higher frequency and voltage and of course don't have a bank of batteries in the middle.

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Old 06-14-2014, 07:04 PM   #19
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Our 8KW generator is to big for us. The replacement will be a 6KW. Running the water-maker, water heater and charging batteries is our standard at anchor and that's about 4.5KW. Even there, the water heater takes less than 1 hour and we don't make water every day.
Same boat, a Krogen 42, with all the toys and two larger chargers (135 amps and 105 amps) and still the 8kw is never loaded.

Have friends who run air conditions with windows open to load the generator.

There is nothing wrong with managing your power load, i.e turn off the water heater if your wife is going to turn on a hair dryer.

Save money in the initial purchase, and in continuing operation by getting a generator sized for what you need. Spend it on drinks for your friends.
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Old 06-14-2014, 07:07 PM   #20
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We haven't talked about size, much. One poster said buy big. I totally disagree.

David
I dont know David

From the engine prospective...Its the same argument about having engines in a boat capable of semi displacement speeds and running the boat at displacement speeds. Or the engine in my F-350, yet I almost never tow anything anymore. I've not seen any real data indicating lightly loading a modern engine is harmful, especially with the bursts of higher loading inherent in power production. Remember that every backup generator in this country is very much oversized due to NEC requirements. There is some fuel savings but not as much as people think. Especially when you consider how much you really run your boats generator.


From the generator end prospective I can say that its better to run a lighter load on a generator end. Oversized generator ends last longer. Here's why...

A generator end is rated by the manufacturer at a certain KW at a certain temperature rise. It can produce and is rated at a higher KW at a higher temperature rise. Once enough KW of load is applied then the manufacurer derates the generator to standby only service.

Generator packagers have a strong financial incentive to use the smallest generator end they can get away with. That means that at their rated output they are running the highest internal temperature RISE that the manufacturer recommends. Manufacturers use temperature RISE as their measurement because they cannot control the ambient temperature the generator will be operated in. Think of how hot it is in your generators sound shield, in your lazerette, on a hot day in the heat of summer. Then consider that you are loading the heck out of that generator. Bigger is cooler running, increasing lifespan.

There's also another issue that makes larger better. That is the ability to handle a sudden load. When a large load is applied the engine decreases RPM. This also makes voltage fall off because voltage regulation is not a perfect science, it is frequency dependent. The governor senses the decreased frequency and increases the throttle setting. The engine increases in RPM and the governor senses that and decreases the throttle. These processes take time. Time to sense the falling frequency. Time to move the throttle, time to deliver more fuel. A larger engine and generator end create more rotating mass, making them inherently more frequency stable.

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.


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Kevin...

What's the deal with inverter type gensets like the little Hondas?

Someone asked awhile back and can't remember if you jumped in and explained why we don't see more versions of the type in permanently mounted sets.
I love the little hondas. Great little generators. Reliable, inexpensive. I cant think of anything wrong with them except they are not built in.

As to why there are not more generators like that I have no clue. Probably as was suggested R&D money.
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