Engine Swap Kohler for Onan

[Bodger]

Pulled the original Onan 24 with about 6000hrs and replaced with a 30hp Kohler with about 40hrs.  The engine is a CH750-0003, the same one Cooks uses on their mills.  It came to me used and the owner could not find out why it would not cut.  I replaced an ignition module and it seems to be strong now.  Most of the swap over was pretty straight forward.  The Kohler needed to be shimmed up 2" for the drive shaft to be in the same spot.  Shimming worked pretty good, I didn't have to adjust the belt tension.  The only problems are the muffler is exhausting right on the side of the gas tank (does that sound dangerous to you?) I may just cut it off, flip it and reweld it.  The other issue: there is still some fabricating to do on the throttle linkage.  The Kohler is a lighter motor seems to be noisier. It is made to run @ 3800 rpm as opposed to the Onan's 3600.  I don't want to sacrifice torque for speed so if you have any wise input that will help please speak up.  I ran a couple of pretty good size logs this afternoon and it cut well.  It turned out to be about an 8 hour job.  Had to buy a few parts: New pulley 1 7/16", springs and some wiring.  I took the pieces of steel to the machine shop and had the holes slotted so I would have some room for adjustment. 

[Chuck White]

I would definitely do a retrofit on the exaust system!

[Bibbyman]

You put this on a Wood-Mizer?   WM may be able to help you with linkage parts.  We once swapped out a Briggs and Statton for an Onan and WM helped out with linkage parts.

[Bodger]

Bibby, I called WM and they said the throttle set up comes on the engine they sell and it uses the same linkage as the Onan...I've got it rigged up to operate but will tweek it and fix something more permanent after I run it a little to be sure of what I need.

[Bodger]

Here is an up date for anybody that may be interested in making a swap.  First off, WM has been very forthcoming with information concerning engine swaps.  Thank you for your input, gentlemen.   I've run a couple of weeks now with the new Kohler 30hp cutting around 2k per day.  I'm still working out the dynamics of blade speed but the lumber looks just the same, very good.  The Kohler is a little lighter than the Onan and that makes less strain on the up/down motor, so my up speed has increased a tad.  Gas mileage is better, I'm using about a gallon and a half less per day now.  I flipped the exhaust (cut off the pipes and re-welded facing away from the gas tank).  This engine doesn't seem as industrial as the Onan but I believe it is the deal.  Going up six hp (from 24 to 30hp) requires getting a new feel for when a blade gets dull...the 30hp will push one longer.  I still have to fabricate something for the throttle...I've got one cobbled together that is working but not exactly what I want to live with for an extended time.  I will make the final decision when I finish the rebuild on the Onan...keep the Kohler or put it on the market and replace the original engine.  I'm not trying to get anybody to go around WM for a replacement engine but if you have one fall into your hands (as did this one for me) I would say it is doable and not that complicated.