Might have one of these available to me in visually clean but unknown functional condition.  I've been looking for a small(ish) diesel generator though and so it seems like a good idea, as long as it works or can be brought up to operating condition at a practical cost in dollars and labor.  Also some general idea of what it's worth so I can make a reasonable offer on it.

As an aside it supposedly does 120/240VAC as well as 28VDC... wonder if there'd be any way to convert it to 13.8VDC.

there are several ways of dropping the DC.  The question for you is what is your amperage requirement from it, and how exact do you need the voltage to be.

If you are going to charge 12 volt batteries, simply charge two of them in series at a time.  Otherwise you will need a regulator.  You can rig a simple one with high current diodes from radio shack if you have no other options, but there are better ways of doing this depending on your current needs.

Edited to add, if you just want to run a laptop, a regulator should do it fine.

a 3600 rpm diesel seems to defeat at least some of the purpose of getting a diesel - usable power output at low rpm, which equals longer life.

northerntool has a selection of diesel gensets.

a 3600 rpm diesel seems to defeat at least some of the purpose of getting a diesel - usable power output at low rpm, which equals longer life.

Just a note- Diesel generators don't run at variable RPMs like tractors, air compressors, welders, etc.  That have to run at 1800 or 3600 rpms to generate 60 Hz power (some huge generators may run slower.)  The RPMs time the number of pole pairs allways has to equil 3600 (ther number of cycles in a minute).  The exception is in inverter based generators or locations useing 50 Hz power.

But yeah, the 1800 rpm generators are quieter, vibrate less, and last longer, but are slightly less fuel efficient.  But a 3600 rpm Yanmar will outlast a honda anyday, which will outlast almost anything else portable.

The part number I got off the manuals that supposedly went with the unit, they describe a diesel powered generator and that's what the person who has the generator says they are.  He said they were made by Onan.  I didn't get a chance to look it over closely, I did get an overall photo of the unit though if it would be helpful.  I'll try to check back with him and get a look at nameplate, etc.

One of the reasons I was looking for a diesel is quieter running so if it's a higher RPM and noisy that would not be as good.

I did notice that it has a single battery for starting so it's a 12v starter (or so it would appear).