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Old 04-25-2017, 01:00 PM   #1
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Two Generators

Our Defever44 came with two generators which, I believe, were original to the boat. One is a Perkins-powered 12.5Kw Kohler. The other is a 7.7Kw Westerbeke. Both have about about 2,400 hours usage. Having two generators is nice for redundancy and using the smaller one is more efficient for lower power demands. However, that second generator takes up a lot of space. I am seeking opinions. Should I have the Westerbeke removed or should I keep it? Th Westerbeke is extremely difficult to service. To replace the raw water pump impeller, the alternator must be removed to get at the pump which also must be removed. Wrenching all of it out of there is a bear so I am much inclined to just get rid of it.
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Old 04-25-2017, 01:17 PM   #2
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My first impression is that I am not inclined to remove things from the boat.

That said, I think the two generator concept is a bit more applicable to boats larger than your 44' aft cabin. With careful load managment I do not see where your 12 KW could not handle the loads without being underloaded.
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Old 04-25-2017, 01:24 PM   #3
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Do you already have a large house battery bank and inverter/charger?
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Old 04-25-2017, 01:46 PM   #4
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Quote:
Originally Posted by High Wire View Post
Do you already have a large house battery bank and inverter/charger?
Yes. Magnum 2812 inverter-charger feeding eight (8) 6-volt golf car batteries, 920 amphours.
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Old 04-25-2017, 01:55 PM   #5
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I have 2 14kw generators, it's nice to have a spare. But as High Wire alluded, an inverter with a good battery bank is also a backup.
Since I ditched the electric stove, added a better inverter, my power needs dropped considerably. Should I choose, I can charge the house banks with the mains. I only need the high output if rafting and supplying power to others.
Another method for servicing your generator, mount it on sliding rails if there is space to slide out. In service, bolts secure the rails but are removed to slide. It requires slack electric, fuel and water lines, and easy disconnects on the exhaust, etc.
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Old 04-25-2017, 02:11 PM   #6
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I have long thought about a similar setup. Rather than a larger 7.5-10K, it would be nice to have a 3K and a 5K, for example. (Obviously sized will vary based on the overall size of the vessel and power demands).

It is my understanding they size the generator for a 'worst case scenario' where a Heat/AC, stove/oven, water heater, battery charger are all running at the same time. However this is rarely the case. In most cases, I'm just recharging the batteries. In this case, the load on the generator is low (to low??).

It would be nice to be able to fire up a 3K for light loads. A 5K for medium loads, and both for heavier demands.

This leads to a question.....

Can you have two generators running together? If so, do you need to split the circuits those generators are feeding?
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Old 04-25-2017, 02:23 PM   #7
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I believe in simplification, but removing it won't be an easy task either, including all the wiring/switches etc....

Good question though, no easy answer...
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Old 04-25-2017, 03:01 PM   #8
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If you're happy with the Kohler, I'd remove the Westerbeke.

You can't have too much space in the engine room.
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Old 04-25-2017, 03:15 PM   #9
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Quote:
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This leads to a question.....

Can you have two generators running together? If so, do you need to split the circuits those generators are feeding?
You can run both generators at the same time IF there is ABSOLUTELY NO WAY to connect the outputs together. The AC waveforms of the outputs must be exactly matched before tying them together or else one or both generators will be catastrophically destroyed.
Its called "paralleling" the generators. Larger machines can be paralleled with a Synchroscope and remotely controlled output breakers. High dollar megayacht stuff.

In todays marine generator market for smaller powerboats it is not available. Honda Inverter series portables can. Maybe someday their inverter technology will spread to installed marine gen sets for yachts.
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Old 04-25-2017, 03:33 PM   #10
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Mr Murphy will frown on you if you take out your backup gennie. Next cruise afterward, the Kohler will poop. Just the way things seem to work. Highly technical, I know.

On a serious note, I would rather have one brand new gennie than two old ones. For numerous reasons, gennies can be way more of a PITA than main engines. Perhaps you could sell both as running proven takeouts, and offset the cost of a new one.

If you want to keep the old Kohler, keep the Westy too.
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Old 04-25-2017, 03:41 PM   #11
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If you have the room keep both. I would love to have a backup to my Westerbeke 8kw. If I were starting from scratch I would have two smaller generators.

Having almost faced the necessity of replacing my generator (ouch!) to have two on board so that if one fails I didn't have to buy another one would be wonderful.
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Old 04-25-2017, 03:41 PM   #12
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If you're happy with the Kohler, I'd remove the Westerbeke.
Or the other way around. Do you REALLY find many chances to load up a 12.5KW genset? I struggle to put a decent load on my 7.5KW.
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Old 04-25-2017, 03:54 PM   #13
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Or the other way around. Do you REALLY find many chances to load up a 12.5KW genset? I struggle to put a decent load on my 7.5KW.
I agree but I'll leave the loading question to the OP, Catalinajack. I believed he's owned the boat for awhile.

We have an 8kw Northern Lights on Hobo. If it were to die, I'd put their 6Kw in as the replacement. I would like to load the 8kw more than I do.
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Old 04-25-2017, 04:16 PM   #14
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I would be happy with a 6KW instead of an 8KW, but my 8KW is a slow speed (1,800 RPM) and most of the smaller units are high RPM (noisier ).

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Old 04-25-2017, 05:41 PM   #15
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Plenty of 1800rpm 3cyl 5-6kW machines available. NL, Westerbeke, other brands.
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Old 04-25-2017, 06:17 PM   #16
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Or the other way around. Do you REALLY find many chances to load up a 12.5KW genset? I struggle to put a decent load on my 7.5KW.
On our DF loading up the 12.5 is not a problem. Reverse cycle air, washer, dryer, battery charging, all electric galley and water heater will max it out.
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Old 04-25-2017, 06:36 PM   #17
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I removed two generators, a 7.5 Onan and a 2.5 Mase. Both were running, sold as running take outs. Both were an unpredictable expense waiting to bite me at an inconvenient time IMO. I do have a Honda 2000 that I sometimes use, I run it every 3 months whether I need to or not.

Should the OP remove one or both his? All depends. Start out with a blank spreadsheet (or sheet of paper if you enjoy math) and list your loads to determine average and peak loads, and Ah consumed per day. After that it is easy: right sized alternators, house bank and inverter, solar panels will do it if you don't want/need aircon.

In my case: 2 x 200A Leece Neville alt, 1284 Ah AGM house bank, 3000 VA inverter/charger (prob should have been 5000) and 2070 W solar. I occasionally use the washer at anchor (sunny days), but only run the dryer when on the move. Propane cooktop. Webasto hydronic heating, loops for hot water via Webasto and engine.

Whether 2,1 or 0 gennies work for you will depend on a full systems review.
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Old 04-26-2017, 06:32 AM   #18
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You could always run the proper engine pickeling procedure and just forgetaboutit.
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Old 04-26-2017, 09:19 AM   #19
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We have a 5.5kw Northern Lights and that runs at 1800, they now call it 6.0kw. Been very happy with it, handles everything we need.
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Old 04-26-2017, 09:49 AM   #20
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I have known a couple of boats where the captain felt he had a hard time loading his 12kw generator. Thus when he wanted to use the washing machine he also turned on one of the AC units to cool an empty section of the boat.

Our 8kw runs everything. We do exercise power management. Chiefly in the first ten minutes of generator run when both chargers and the water heater are running at max. We do not then also turn on a hair dryer and/or the microwave. If necessary I have turned off one charger or the water heater for 10 minutes.

I can tell when the load is affecting the generator. I have a frequency meter which reads the output. A drop from 60.5 hertz to 57 hertz is enough of a load for me. i will not then add more load.
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