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Old 10-04-2012, 01:11 PM   #21
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Thanks Moonstruck and Norwester for your comments on the Nextgen generator. I think this is the way I will go if I even do it.

Ron
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Old 10-04-2012, 02:18 PM   #22
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I'm in the process of moving our house batteries and reinforcing the shelf for the instal of a Next Gen 3.5. We should have it up and running soon. I have been researching small generators for the last two years and finally settled on the Next Gen based on owners feedback, the compact size and weight. We also chose the sound shield. Once the unit is installed we'll post it on our Beach House blog. Chuck
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Old 10-04-2012, 05:42 PM   #23
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Originally Posted by Tidahapah View Post
Over the last 17 years I have had 3 gen sets on Tidahapah.
2 x 3000 RPM 240 V 50 Hz
and the last one a 1500 RPM 240 V 50 HZ unit.
The 1 st 3000 RPM er I wore out in 3 years. Rebuilt it but did not reinstall it instead made the drastic mistake of buying another 3000 RPM er, (Kubota engine) wore it out over the next 5 years.
Have since installed a 3 cyl Perkins driven Stamford 9 KVA gen set that now has 4000 hrs on it and going strong. Just recently did a cyl head O'haul just because I had some down time.
Would not ever consider a high reving gen set again.
Really like the MASE gen sets, very quiet and well built with Yanmar engines.
One of these would be my next choice if required.
I'll bet the high speed gen set engines died from excessive under loading .. Not from high engine speeds. This is the only application where underloading can be a real probable threat. Each power stroke requires less force w higher rpm or more cylinders. An engine run properly should last long enough so it would be impossible to wear it out no mater what rpm the engine operates at. If one could run an engine 15000 to 20000 hrs a lower speed engine may or probably would outlast a slower turning unit but pleasure boats just don't accumulate enough time to wear out properly run engines whether as a prime mover or as a gen set. A high speed engine may SOUND like it's over stressed but if one considers the forces on the parts of the engine like piston speed and BMEPa smaller engine turning faster may be dealing w less stress. I had a Nissan diesel car once that sounded terrible at low engine speeds and got very noticeably quieter w considerably more throttle (load) .. a big difference actually. So much of the time what an engine sounds like may be very different from how "happy" it is or how much wear is taking place.
So the idea that an engine turning faster will wear out quickly is in general just plain bunk. Obviously ther'e will be exceptions and taken to extremes what I'm saying is just plain bunk. Huge very slow engines last much longer than small high speed units but within the realm of what we use in trawlers almost no engine will accumulate enough hours to wear out so this question is of little or no interest to trawlermen.
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Old 10-04-2012, 06:11 PM   #24
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I agree with ManyBoats at post #23 in principle. One often reported issue is that high rpm engines of the type mated to small gensets are not as well built, so ManyBoats is right that rpm is not itself a source of shorter life but poorer build quality certainly is.

Also: what about noise? Are hi rpm units inherently noisier than 1800rpm gensets?
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Old 10-04-2012, 06:29 PM   #25
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I agree with ManyBoats at post #23 in principle. One often reported issue is that high rpm engines of the type mated to small gensets are not as well built, so ManyBoats is right that rpm is not itself a source of shorter life but poorer build quality certainly is.

Also: what about noise? Are hi rpm units inherently noisier than 1800rpm gensets?
I don't really know but I think load is more a generator of noise than rpm. And design features like composition chamber shape and valve gear design effect noise. As per the Nissan diesel auto engine engine noise can actually reduce w more load. So there are many variables. Much of the time vibration causes most of the noise in a boat and lower rpm or fewer cylinders will increase vibration at the same power output. But re the OP I think engine rpm in both propulsion and gen set engines is completely a non issue.
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Old 10-04-2012, 09:09 PM   #26
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So the idea that an engine turning faster will wear out quickly is in general just plain bunk.

You're incorrect about that. Not bunk just incorrect. I have direct hands on experience in this area

A industrial quality 1800 RPM diesel generator engine will generally go something between 20 and 30,000 hours, if it is run at a reasonable loading rate, and otherwise maintained properly.

A industrial quality 3600 RPM generator set might go 5,000 hours but thats honestly pretty few and far between.

I see it with my own eyes. Take a yanmar small diesel and spin it 3600 rpm in a light tower, its a 5,000 hour engine at best. Take that same basic engine and spin it at 1800 RPM and its a 20,000 hour engine conservativly.

That said I would argue in a recreational marine application its for the most part irrelevant. Most recreational generators are infrequently used, and run with almost zero preventative maintenance except oil changes. couple that with a corrosive enviroment and you are setting the engine up for a premature failure.

You really want to see an engine last, look into the generators in the oil field. We have units that typically go 7-10 years of continous duty running with the only shut down for maintenance. Why do these units last so long? They turn at 1200 RPM. Some units that pump oil turn at 600 RPM and can last a lot longer than that. Years longer.

Engine life is very much related to engine speed, but in a marine enviroment where few engines actually wear out having died before their time due to a catastrophic failure, does it really matter?
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Old 10-05-2012, 06:35 AM   #27
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"Engine life is very much related to engine speed, but in a marine enviroment where few engines actually wear out having died before their time due to a catastrophic failure, does it really matter?"


What does matter more is fuel consumption.
A few folks I have talked to that removed antique OHNO or Koller diesel units found the fuel consumption WENT UP when the new units were operated as usual on small boats , at light loading.

Some were normally left on a few hours after meal service to run the reefer and charge the batts .
They found the fuel consumption at these minor loads to be about double their removed antiques fuel burn.
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Old 10-05-2012, 09:04 AM   #28
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At my current usage, it looks like I'll need to replace the little Yanmar in the Mase Generator in 2028. More to worry about
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Old 10-05-2012, 10:52 AM   #29
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Originally Posted by Capn Chuck View Post
I'm in the process of moving our house batteries and reinforcing the shelf for the instal of a Next Gen 3.5. We should have it up and running soon. I have been researching small generators for the last two years and finally settled on the Next Gen based on owners feedback, the compact size and weight. We also chose the sound shield. Once the unit is installed we'll post it on our Beach House blog. Chuck
Moving the batteries to make room for a genset is a great idea, Chuck. What expectation do you have for the number of hours you'll get out of the genset?
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Old 10-05-2012, 12:36 PM   #30
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Kasanders,
OK, I'll buy that but I may be confusing "high rpm" for medium speed like the 3000rpm engine in my boat w lighter weight 3600rpm units. My propulshion engine would run at 1800rpm as a gen eng. I really don't have any experience w higher speed engines except a 3400rpm Yanmar. Those Yanmars seem to last in the little Albin's but then again nobody runs them enough hours to kill them.
So I'll take back what I said about the little gen sets but I don't see a higher rpm Volvo or Yanmar propulsion engine as having a short life as a result of it's higher rpm running. But perhaps I'm wrong about that too. But that should be another thread if it should be discussed at all.
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Old 10-05-2012, 01:02 PM   #31
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Moving the batteries to make room for a genset is a great idea, Chuck. What expectation do you have for the number of hours you'll get out of the genset?
I don't know about hours but we expect to get many years out of the Next Gen while doing some extensive cruising. Chuck
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