I haven't, but I've been thinking about how to install a couple Chevy L79 engines, but with only one inlet on the head, I'm not certain how to get full horsepower out of the 327 engines.

More seriously, I've not run into a limitation with my 14 HP Kohler, so I'm good with mine. If I did add a different engine, I would only do it if I could find some other reason aside from power. Fuel flexibility, maybe?

One thing I would think of is getting some flywheel or something, so the RPMs don't drop when running into a pine knot or something.

Using the LM29, very satisfied of the Honda 13hp engine, don't feel the need to change. Recently saw a 28 inch white oak log, did fine even on such a task!

I have a 15HP Kohler on my LM2000. I wish I had bought the 23HP Briggs originally, but I'm o.k. with the smaller Kohler. It's a good motor with few problems -- a little slower, but it handles everything I put to it.

I got a good price for a 20 hp Honda so I stuck it on my mill to replace the 13 hp.

Your situation with LM 29 remembers me a story, when couple of moths ago, we were trying to buy some serious equipment for wood-processing near Atlanta, but only we were looking for financing help, and it was much harder.

Has anyone used an electric motor on the lm29?

It's been a while since the question was answered, but I happened to have a new 22hp harbour freight "Predator" engine sitting around, and just wasn't happy with the 13hp that came with my mill. I was a little concerned that the bigger engine would be too heavy for the carriage, but everything just bolted down [had to make some changes to allow for the throttle and choke] and I haven't looked back since. The electric start is sure nice; allows for shutdown while I roll the log or move boards and a quick restart by turning the key.