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Old 12-09-2012, 16:52   #1
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Marine Diesel and a strap on generator

Couldn't think of any other way of describing it.

Most everyone on here has said if I want a diesel genny the only real way to go is have a dedicated watercooled marine diesel genset.
Cost is prohibitive for the small enclosed units (bang for buck is not there for me)
And the thought of having an additional engine when I already have 2 seems a bit silly.
Not to mention expensive and heavy.

Is there any reason why I cant have a strap on, like a HUGE alternator?



I understand that running a diesel without load is apparently not good, so using them for charging alone with the 100amp alts I already have fitted would not be something I would do, but what about something along the line of a 10kw - 12kva belt driven generator?
Would that put sufficient load on?

Has anyone done anything like this before?
Can it be done, Silly idea or not
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Old 12-09-2012, 17:03   #2
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Re: Marine Diesel and a strap on generator

i have a 3.5 kva 240v belt driven generator off the front of my 140 hp engine,set the revs at 1600 and we have power whilst motorsailing.

dont know if it will put much of a load on unless you are running lots of stuff.
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Old 12-09-2012, 17:05   #3
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Re: Marine Diesel and a strap on generator

I will just point out a couple of downsides that I see; you can work out the upsides .

The AC frequency will be dependant on the RPM of the generator thus dependant on the RPM of your engine. These units are normally used on a speed governed engine.

This is a lot power to belt couple, I would be concerned about the belt setup (and pulley ratios will affect RPM, thus frequency).

It doesn't LOOK like it would handle a marine environment.

But anything is possible if you throw enough time / money at it
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Old 12-09-2012, 17:21   #4
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Re: Marine Diesel and a strap on generator

Why not just look around on the internet for the real thing.
Here is one running and a spare starting at $450

KOHLER DIESEL MARINE GENERATOR | eBay
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Old 12-09-2012, 17:25   #5
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Re: Marine Diesel and a strap on generator

I don't know how heavy duty your 100 amp generators are, or how big your battery banks are but would it not be possible to charge a largish battery bank and use a big inverter to supply the power?

My recent experience suggests that running the main diesel to charge batteries is more pleasant than a small petrol generator, and the costs look similar.

If you need continuous AC then a Honda could be the way to go.

I'm not sure that diesels like a heavy load when starting.
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Old 12-09-2012, 17:27   #6
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Re: Marine Diesel and a strap on generator

Quote:
Originally Posted by Wotname View Post
I will just point out a couple of downsides that I see; you can work out the upsides .

The AC frequency will be dependant on the RPM of the generator thus dependant on the RPM of your engine. These units are normally used on a speed governed engine.

This is a lot power to belt couple, I would be concerned about the belt setup (and pulley ratios will affect RPM, thus frequency).

It doesn't LOOK like it would handle a marine environment.

But anything is possible if you throw enough time / money at it
no problem with running it in the engine room in regards to the marine environment.

pully off the front of the engine is a 16cm diam to a 8 cm on the genset providing 3600 rpm with the engine running @ 1600-1650.rpm
needs twin belts,but never got round to getting a 4th slot madeup off the engine,so it chews the single belt after about 100hrs.

getting the hertz and voltage setting right i have a 2 meters volts and hertz near to the helm on my main house switchboard makes it very easy to set the revs, also a power cut off switch if i need to increase or decreas revs suddenly.

the generator is mounted on a hinged plate next to the engine with a bottle screw to tension,or let the belt slip free if im not using it.
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Old 12-09-2012, 17:45   #7
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Re: Marine Diesel and a strap on generator

Quote:
Originally Posted by Cotemar View Post
Why not just look around on the internet for the real thing.
Firstly because in the op I said I do not want a 3rd engine or the additional weight.
Secondly because I live in Australia and this sort of thing is near non existant, though I did look at one the other day a 37hp turbocharged yanmar with an 11kva bolted to it

Seems ridiculous having something that size in a boat that has 65hp as the primaries plus I simply dont have enough space in the engine-room for 2 motors and still have the space to work on them.
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Old 12-09-2012, 17:49   #8
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Re: Marine Diesel and a strap on generator

Quote:
Originally Posted by atoll View Post
no problem with running it in the engine room in regards to the marine environment.

pully off the front of the engine is a 16cm diam to a 8 cm on the genset providing 3600 rpm with the engine running @ 1600-1650.rpm
needs twin belts,but never got round to getting a 4th slot madeup off the engine,so it chews the single belt after about 100hrs.

getting the hertz and voltage setting right i have a 2 meters volts and hertz near to the helm on my main house switchboard makes it very easy to set the revs, also a power cut off switch if i need to increase or decreas revs suddenly.
All pretty much what I was thinking

Have you got any pictures on the setup?

Quote:
the generator is mounted on a hinged plate next to the engine with a bottle screw to tension,or let the belt slip free if im not using it.
I was thinking similar but with a Highfield lever for tensioning

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Old 12-09-2012, 17:57   #9
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Re: Marine Diesel and a strap on generator

I see no problem.... if it's an AC unit you must run it a specific rpm though... really specific!
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Old 12-09-2012, 17:58   #10
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Re: Marine Diesel and a strap on generator

Quote:
Originally Posted by cat man do View Post
All pretty much what I was thinking

Have you got any pictures on the setup?


I was thinking similar but with a Highfield lever for tensioning

being able to let the belt go slack when not in use saves alot of wear,plus my engine will rev up to 3200 rpm so that would be 6400 on the genset if i left it engaged!

the beauty of a bottle screw,or even a threaded bolt is that you can increase tension with it running if the belt is slipping.
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Old 12-09-2012, 18:00   #11
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Re: Marine Diesel and a strap on generator

Quote:
Originally Posted by Boracay View Post
I don't know how heavy duty your 100 amp generators are,
Just 100amp Bosch alternators, nothing special

Quote:
or how big your battery banks are but would it not be possible to charge a largish battery bank and use a big inverter to supply the power?
Plan (guessing) on around 800amp hour with a fair amount of solar and sure, I will get plenty of juice while on passage, but if parked for weeks at a time with possible rain periods an cloud I need something else to keep the power up for a power hungry fridge freezer (household size 240v with inverter or inefficient 12v also household size) , 40inch monitor and occasional air con usage

Quote:
My recent experience suggests that running the main diesel to charge batteries is more pleasant than a small petrol generator, and the costs look similar.
Nice to know

Quote:
If you need continuous AC then a Honda could be the way to go.
Fuel is part of the issue
Dinghy has a 20hp on back, if I am away for weeks at a time I am not sure I will have or want to carry enough fuel for running both.

But I haven't discounted the idea of a Honda totally, just figure I would rather keep it all in the engine room using the fuel I have an abundance of with motors I already have.

Quote:
I'm not sure that diesels like a heavy load when starting.
I think atoll has taken care of that issue.
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Old 12-09-2012, 18:05   #12
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Re: Marine Diesel and a strap on generator

Quote:
Originally Posted by atoll View Post
being able to let the belt go slack when not in use saves alot of wear,plus my engine will rev up to 3200 rpm so that would be 6400 on the genset if i left it engaged!

the beauty of a bottle screw,or even a threaded bolt is that you can increase tension with it running if the belt is slipping.
That's what electric clutches are for!
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Old 12-09-2012, 18:23   #13
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Re: Marine Diesel and a strap on generator

If it's put together right it will be reliable. Driving accesssories with V-belts is well proven. I'd definitely use 2 belts, the A size (nominally 1/2" wide). The AX type, with a notched v part is a more efficient belt.

Electric clutches are very convenient, so long as you don't spill salt water on them. Mechanical, like your Hyfield lever, is very reliable.

It's surprising sometimes the amount of vibration/load an accessory like this can see. Make the mounts very solid. In case of doubt, over do this area.

Good luck with it,

Paul
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Old 12-09-2012, 18:53   #14
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Re: Marine Diesel and a strap on generator

Quote:
Originally Posted by Pauls View Post
If it's put together right it will be reliable. Driving accesssories with V-belts is well proven. I'd definitely use 2 belts, the A size (nominally 1/2" wide). The AX type, with a notched v part is a more efficient belt.

Electric clutches are very convenient, so long as you don't spill salt water on them. Mechanical, like your Hyfield lever, is very reliable.

It's surprising sometimes the amount of vibration/load an accessory like this can see. Make the mounts very solid. In case of doubt, over do this area.

Good luck with it,

Paul
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Old 12-09-2012, 19:01   #15
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Re: Marine Diesel and a strap on generator

what you really want is one of these bad boys!
which will produce constant ac and stable freq at variable revs!

Variable speed generator for alternative energy systems

http://www.synchrotek.net/products.php
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