Not sure i'd recommend a 6 cylinder inline.
What you need is an industrial engine with a govenor. The issue with a standard engine is it will not react properly when loaded down. You will set a speed then when you drive it will bog down, you want it to hold that speed like a lawn mower engine does.
I had a mate that had a V8 hooked up to a welder, he said it didn't have a govenor and you'd start welding and you'd almost pull it to a stop. You need the govenor to give it more throttle when loaded down, less when idle to maintain the speed.
Personally i'd look at a kubota on ebay, they are inline 4 cylinders, 2.2 litre and about 50 or so HP
I hear what you are saying regarding a motor with a governor and I'm in luck..
I have an industrial Ford 200 (out of a swather)
Industrial Ford 200 -- PhotoBucket Album
And (2) industrial 300's (one is complete out of a 9 wheel dirt packer)
Industrial Ford 300 -- PhotoBucket Album
I also have operation and repair manuals for both.
So I have reference material galore.
The skidsteer came with a belt driven governor from a Massey Combine.
Lets say I have a bit of a hording problem and that I like FordSixes..
I've got the following
All of these motors share the same bellhousing pattern, small 8.5" flywheel or C4.
(1) 144 (1960 doesn't run -- the rest do)
(1) 170 (1970 )
(4) 200's (67, 68, 77, 78)
Additionally I have the following which all share the SBF bellhousing
(2) 250 (1975 -- both of them)
(1) 240 (1965)
(4) 300's (75, 76, 78, unknown dirt packer has E7 casting code so no older than 87)
I'm going to make the bellhousing plate to accommodate the SBF pattern with a 157 tooth flywheel or flexplate. I make parts as needed. I have created small i6 motor mounts for Ford Unibody cars
Ford Small i6 Motor Mounts -- PhotoBucket Album
I've also created an adapter that lets me use a small i6 motor with a SBF bellhousing
Small6_SBFAdapter -- PhotoBucket Album
So, I am not going to even going to seriously consider a diesel.
I own a Ford 6.0L Powerstroke and I know very well what to expect with them and what to pay attention to when they aren't acting correctly, but I am completely unversed on Kubota diesel operation. I have no idea what models are available. I have no spare parts for them, no idea if I need specialty tools for diagnostics or repair, and I'd have to buy one to begin with.
I did out of curiosity, look at eBay for Kubota 2.2L
they were either new and $5,000 or used and $1300. And I'd still end up buying a starter, alternator, figuring out how to hook up the throttle and creating a bellhousing and motor mounts. I admit a small diesel will run more efficiently and would probably package nicer but there is simply no way I'd ever recoup the initial investment costs.
I think I may have this rich text editor finally working, so I'll go start a repower thread now.
Small6_SBFAdapter -- PhotoBucket Album