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Old 15-09-2015, 23:21   #46
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Re: DC genset to power boat.

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Originally Posted by typhoon View Post
My DC generator design address all the pitfalls you describe. I kept it as simple as possible . Of course you do have to have the space . Been working great so far . I am surprised how little fuel it consumes .
That's an awesome setup! Thanks.

I've got a Phasor Marine 5.5 kW generator with about 3500 hrs on it and I'm fully expecting the AC end to go well before the Kubota! I had been kicking around a similar setup for when it goes, but using another high output alternator (135 amp / 24 Volt) like the one on the main engine for redundancy and minimizing spares. It would certainly simplify the charging system. It'd be easier to do with belts, but I haven't found much info on how much side load the back end of the Kubota is good for. That size would be fine for us as with the solar (820 watts) I've got, we find we're only running the generator a couple hrs a week during cloudy periods or when running the washing machine at anchor and about an hour every day underway. Our watermaker is 24 volt and runs 75% or more of the time off solar.

I've also been sketching up a configuration with the alternator and the dive compressor (with a clutch setup) on the Kubota as the dive compressor is the one item on board that I'd probably struggle to run off the inverter. A configuration similar to yours is probably better for that.

Just one thought on your setup. A 'splash hood' over the alternator may be something to look at when you start using the watermaker. Will any inadvertent hose leaks, etc drip into the alternator with the current configuration?

You've certainly given me some food for thought!

Thanks,
Mark
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Old 15-09-2015, 23:52   #47
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Re: DC genset to power boat.

Multiple side loads can be located opposite each other so that they cancel side loads on the engine.
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Old 16-09-2015, 06:54   #48
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Re: DC genset to power boat.

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Multiple side loads can be located opposite each other so that they cancel side loads on the engine.
As long as they are both *active* at the same time....??
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Old 16-09-2015, 10:50   #49
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Re: DC genset to power boat.

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I am considering putting a DC generator together also.

Putting aside the arguments for or against it, I have two 3 cylinder diesel engine's available to me for this. One is a Kubota D850 rated at 15 HP @ 2500 rpm and the other is a Yanmar 3TN66CEJUV rated at 14-17 HP @ 3350 rpm.

I want to be able to power a large alternator (200 amp +), a water maker pump and a refrigeration compressor.
The Yanmar is considerably smaller, at least 3 inches in all directions. I believe I could make either one fit but I like the smaller footprint of the Yanmar.

Which of these engines would be the best choice and why?

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I did what you are talking of with a 3 cyl Kubota. Water maker + 150 amp alternator. I learned a couple of lessons to pass along:
1) Pick an engine with a flywheel. My model didn't have a flywheel.
This cause too much vibration to be passed to the aluminum frame I fabricated. I think it was a harmonics thing, but it also caused a multi sheave V belt pulley to come apart! I couldn't feel it in the boat but it was in the engine and frame.
2) I used V belts and they were very short to make the whole thing compact size. These are hard to find and a little bit of length difference makes a big change. Mount your alternator as Direct Drive! This will eliminate pulley and belt issues.
3) Use an adjustable vernier throttle control. They sell these "aircraft" type controls pretty reasonable and you can find the sweet spot and rpm that makes the unit very quiet. I found I could run very low rpm after the initial 15-20 mins of high amp output. Actually I never ran at very high rpm at all.
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Old 16-09-2015, 11:00   #50
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Re: DC genset to power boat.

Considerations when deciding on an engine. How will you control RPM with varying loads . How will you belt a high output alternator on a small engine , the side loads on are very high when producing over 200 amps , say goodbye to the end crank bearing . You don't want it running over 1800 rpms , they make a lot of noise and need an encloser inside the engine room and don't last as long . Look for engines with at least 3 cylinders they vibrate less . I used an engine that was set up for a generator it has a governor, and drove the alternator directly off the crank , no belts . The Echo Tec alternator was the only one that made serious power at 1800 rpm , so it was a no brainer .

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Old 16-09-2015, 11:39   #51
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Re: DC genset to power boat.

I'd look real hard at a serpentine belt, especially a toothed belt, side load with one of those can be almost zero as you don't have to have it tight, the teeth provide the friction, they can't slip. I don't think you can direct drive a regular Alt like a Balmar as the RPM will be way too low, plus with a belt you can change ratios until you get it right.
Of course funny thing is, I believe an Alternator produces AC current, not DC, so your DC generator really isn't.
The little Kubota single cylinder that Nexgen uses vibrates very little for a single cylinder that is, but all things being equal a three cylinder or ideally a six cylinder will be smoother.

I started down this road and one day may re-visit it, but finally came to the conclusion it was better to buy something that was already out there, that the bugs had already been worked out.
Now what would in my opinion change that attitude would be if I had a free engine or something available, that might temp me.

Makes me wonder why there is no larger AC generators like the Honda's, that aren't tied to RPM to get the correct Hz rate?
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Old 16-09-2015, 12:11   #52
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Re: DC genset to power boat.

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I'd look real hard at a serpentine belt, especially a toothed belt, side load with one of those can be almost zero as you don't have to have it tight, the teeth provide the friction, they can't slip. I don't think you can direct drive a regular Alt like a Balmar as the RPM will be way too low, plus with a belt you can change ratios until you get it right.
Of course funny thing is, I believe an Alternator produces AC current, not DC, so your DC generator really isn't.
The little Kubota single cylinder that Nexgen uses vibrates very little for a single cylinder that is, but all things being equal a three cylinder or ideally a six cylinder will be smoother.

I started down this road and one day may re-visit it, but finally came to the conclusion it was better to buy something that was already out there, that the bugs had already been worked out.
Now what would in my opinion change that attitude would be if I had a free engine or something available, that might temp me.

Makes me wonder why there is no larger AC generators like the Honda's, that aren't tied to RPM to get the correct Hz rate?
Balmar made one for a short time, evidently they abandoned the idea.
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Old 16-09-2015, 12:28   #53
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Re: DC genset to power boat.

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Originally Posted by a64pilot View Post
I'd look real hard at a serpentine belt, especially a toothed belt, side load with one of those can be almost zero as you don't have to have it tight, the teeth provide the friction, they can't slip. I don't think you can direct drive a regular Alt like a Balmar as the RPM will be way too low, plus with a belt you can change ratios until you get it right.
Of course funny thing is, I believe an Alternator produces AC current, not DC, so your DC generator really isn't.
The little Kubota single cylinder that Nexgen uses vibrates very little for a single cylinder that is, but all things being equal a three cylinder or ideally a six cylinder will be smoother.

I started down this road and one day may re-visit it, but finally came to the conclusion it was better to buy something that was already out there, that the bugs had already been worked out.
Now what would in my opinion change that attitude would be if I had a free engine or something available, that might temp me.

Makes me wonder why there is no larger AC generators like the Honda's, that aren't tied to RPM to get the correct Hz rate?
How is side load zero if you are pulling 2? 3? 4? 5? hp on the belt?
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Old 16-09-2015, 13:06   #54
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Re: DC genset to power boat.

Cheechako - The Kubota D850 engine I have was originally from a a welder and the Yanmar was from a John Deere Gator. Both have flywheels. Any preference between these engines? The Kubota just looks more robust but that could just be the bigger size.
I would think the Kubota, having a larger displacement (52.2 ci) would make more torque at lower rpms and be the better choice. The Yanmar (40.15 ci.) seems like it would need to run at a much higher rpm to do the job and with every thing being smaller on it, I would assume the crank bearings would not take as much side loading as the Kubota, but since i don't have the bearing size information, that is purely speculation.

Typhoon - I really like your set up. What engine are you using?
I do intend to drive the alternator directly. I did a quick search on the Echo Tec alternator. Is that really an $1800 alternator?
I know quality costs money but that is quite expensive. I have found some alternators that will put out between 175 -185 amps (14.4 volts) at 1800 rotor rpm in the $500 -$600 range.
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Old 16-09-2015, 13:19   #55
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Re: DC genset to power boat.

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Is this one of those slow deaths that take 6-8 decades?

We see them frequently and have used on for the last 7-8yrs. No you don't want to run it inside the cabin but with reasonable care, it's no more dangerous than a built in unit.

Maybe the difference is it's a yamaha not a honda...

Two types of people have stopped using them.
Those with CO detectors and those who die.
Those with CO detectors notice no matter where on the boat it is placed, CO goes up when using it. I did hear if you put it in your dinghy, and use a long bridle it does not affect CO at all.
Gasoline engine fumes kill, very easily.
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Old 16-09-2015, 13:39   #56
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Re: DC genset to power boat.

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Typhoon - I really like your set up. What engine are you using?
I see in your original post from your project you are using a Yanmar.
Do you know the engine model or displacement? I'm curious if it is the same engine I have.
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Old 16-09-2015, 14:29   #57
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Re: DC genset to power boat.

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I see in your original post from your project you are using a Yanmar.
Do you know the engine model or displacement? I'm curious if it is the same engine I have.
Here you go , Yanmar 3gh. I painted it red epoxy because the white was looking a little tired and all I had was red , so red it is

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Old 16-09-2015, 14:40   #58
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Re: DC genset to power boat.

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Originally Posted by Wind River View Post
Cheechako - The Kubota D850 engine I have was originally from a a welder and the Yanmar was from a John Deere Gator. Both have flywheels. Any preference between these engines? The Kubota just looks more robust but that could just be the bigger size.
I would think the Kubota, having a larger displacement (52.2 ci) would make more torque at lower rpms and be the better choice. The Yanmar (40.15 ci.) seems like it would need to run at a much higher rpm to do the job and with every thing being smaller on it, I would assume the crank bearings would not take as much side loading as the Kubota, but since i don't have the bearing size information, that is purely speculation.

Typhoon - I really like your set up. What engine are you using?
I do intend to drive the alternator directly. I did a quick search on the Echo Tec alternator. Is that really an $1800 alternator?
I know quality costs money but that is quite expensive. I have found some alternators that will put out between 175 -185 amps (14.4 volts) at 1800 rotor rpm in the $500 -$600 range.
Check out the temperatures , once these things warm up the output drops radically , My Echo Tec puts out 265 amps cold and settles in at 210/ 215 amps hot , all day . Check out this video
I use mine to charge my LifePo4 battery bank , this is the toughest load you can put on an alternator this Echo Tec just pumps out the amps as long as you want them . there are no regulators to buy it is built in , you can not externally regulate them , they are on or off , you can have them change the regulator to any set point you want , they made it adjustable by 2v for me but I leave it at 13.9 volts .




The price has actually came down a lot they were 3200$ when I got mine . I was lucky and bought mine for 700$ from a guy who didn't use it in his motor home , lucky me , it was still in the box .

As for the engine , if you have a Yanmar in the boat , go with that. Are either of the engines marinized ?

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Old 16-09-2015, 15:11   #59
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Re: DC genset to power boat.

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How is side load zero if you are pulling 2? 3? 4? 5? hp on the belt?

Side load on a loose belt is low, OK not zero, but well within tolerable limits I'm sure, High side loads come from the excess tension required to keep V belts from slipping.
Or if you felt the need, you could direct drive a shaft supported by pillow block bearings and mount the pulleys on the shaft, the pillow block bearings would then carry the side load, and the engine would have none, point being, don't let the concern of side load stop you, it's not hard to manage.
Most small engines are designed to handle quite a bit of side load as they are meant to be used quite often to drive components like pumps etc via a belt.
Actually the shaft may be useful to drive several components off of different pulley's, shaft giving you space to mount several, I guess you could even use an AC clutch to engage different drives if you liked, depends on how complicated and expensive you want to make the thing.

Myself I don't have the time, time is why I abandoned the idea and just bought something.


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Old 16-09-2015, 15:33   #60
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Re: DC genset to power boat.

Neither of the engines I have are marinized. I will be rebuilding whichever one I choose to use and adding the raw water pump and heat exchanger. I have a Ford Lehmen as my main engine so I am not partial to either of the small diesels I have. I just want to use the best one for the job.

I cant seem to find a hp rating or displacement of your Yanmar 3GH. Any idea what it is?

The Eco Tech alternator really seems to be in a class of its own.
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