24GLX - repower notes

Now that I have had the opportunity to spend some time on the Onan P224 powered 16G with the shop made exhaust, I figured now would be a good time to describe the experience of the engine swap and the results.

1 - It does not sound like a 24G. It sounds very similar to my 818T. Maybe a little more rumble but not much.

2 - The tractor doesn't feel all that different. The Onan is a little heavier but not a lot.

3 - The engine isn't that much bigger and yet it is. Compared to the M18 that came off, it looks to be at least 30% larger. In terms of displacement, it is 50% larger. (42 cid vs 60 cid) It is slightly larger than the B48 but not by much. The 3 qt pan does reduce the engine ground clearance compared to the M18 but the transmission is still lower than the engine. The rear cultivator will still work.

4 - As near as I can tell the rear engine adapter from any B series Onan will work with the P224. Not sure about the CCKA.

5 - I had to drill and tap two 3/8-NC bolt holes in the P224 block. There was a casting depression in the crankcase where the holes should have been so locating the position for drilling and tapping was easy.

6 - The crankshaft on this engine had a long 1/4" slot in it. That meant that the shaft seal in the adapter plate was pointless. To seal the transmission I put some RTV around the OD of the bearing plate. That has worked well so far.

7 - The crankshaft was short by about 3/4 of an inch so I made an extension from an old K301 crankshaft and held it on with a SHCS. A metal lathe made that an easy task.

8 - I tied the oil pressure switch through the ignition. To keep the cranking time low, I added a relay so that when the starter was engaged, the coil received power. Without the added start relay it would take a second or so to build pressure before it would start.

9 - A new throttle cable is required. The throttle cable for the M18 is too short. The original choke cable however is just fine.

10 - Rewiring the ignition relay was easy. I just followed the schematic for the 24G.

11 - I added a 4 wire connector at the engine. I decided to use the same connector used on the 24G. It seemed to make sense should I ever want to remove the engine.


I ran it through some wet grass and leaves. Not once did I feel that the engine was approaching maximum load. I was running my modified 50" deck with the 40" deck pulleys. Just to spin that deck with Gravely blades requires 12 hp. I have spun that deck on a 5665 with a freshly rebuilt engine governed at 3300 RPM, the throttle plate was almost wide open. Held wide open the engine would run up to about 3400 RPM. Dropping the PTO clutch at an idle just spins up the deck. No worries about stalling the engine.

I redid the exhaust system to use 1-3/8" pipe. That actually worked out better than the 1-1/4" pipe. The 1-1/4" exhaust system will be used on my 818T or CCKA when the time comes. I will be ordering muffler guards next week.

This tractor now is on the same class as the Pro16. I have to start it just to listen to it run.

All in all, it was a pretty easy job, exhaust system included. I just took my time and enjoyed the process. My recommendation is that if the opportunity arises, do the upgrade to a P224. It is worth it. It is as significant an upgrade as going from a K301 to a M18.

Two word summary? "Quiet Giant" comes to mind. One word summary? "Sleeper"

I did receive some assistance and parts from a few members here. I do have to thanks them for their help.

Don in Fla. who supplied the chunk of crankshaft
Tom, aka Popcorn, who sold me the adapter plate
Boomer - the used Onan parts guy who supplied the correct throttle pieces and engine guard that the PO lost.
Onanparts - Onanparts.com for the exhaust gaskets, etc.

Pictures to come.