Switch 22hp gas to 18hp diesel, will it be less powerful?

[joe48]

Joe, think you missed this part of his post. "I noticed that the 18.5hp vertical shaft yanmars could be had complete for between $1200 to $1700."

Yep, you're right I did miss that part. Cost isn't much more than a comparable B&S vertical twin, so I guess it's almost practicle if you really have your mind set.
Just make sure we get pictures.
Good luck, Joe

 

[Superduper]

Yep, you're right I did miss that part. Cost isn't much more than a comparable B&S vertical twin, so I guess it's almost practicle if you really have your mind set.
Just make sure we get pictures.
Good luck, Joe

Joe48: the engine isn't here yet so I'll not disclose the exact price I paid but I'm happy to say that it was for less than the range I predicted. An exact gasser replacement engine runs something like $1600 and I'm hoping to find a buyer for the current engine which hopefully will offset the upgrade somewhat.

 

[billbill1]

If it's worth it to you, then go for it. I think you'll be plesantly surprised and have more power than ever. Plus you have a project to work on. I have thought of doing the same on my Wheel Horse but I have a horizontal engine that uses two shafts. I like diesel engines better. Is the engine you bought water cooled? I look forward to following your progress, please keep us informed.

 

[MossRoad]

Mossroad: I know exactly what you mean by buying a new lawn tractor rather than dealing with the swap. But I've been there, done that. Had Murray lawn tractor, became unreliable, tired of changing batteries, tired of tires going flat, tired of rebuilding carburetor, etc. So, bought new Craftsman tractor. Old Murray still sitting in the field (10 years now). Result, new tractor needs new battery every year (fixed by modifying battery tray to accept CAR sized Optima battery), tires go flat every year and slips off rim (fixed by installing new Chev Ag type tires, much beefier and never lost a sip of air since). Now, engine is starting to require annual carb rebuilds, etc... No, I've no great desire to have another one of these in my field. When my toaster goes out, I'll toss that and buy another. But the current tractor deserves a little more patience....

Well, best of luck to you. I like projects and wish you success... take lots of pictures, please. I have a late 60's simplicity that ran the original engine for 29 years. Never changed plugs, air filter, oil, etc... and carb never needed adjustment. It had no charging system, but did have electric start. I just kept the battery on a 500MW charger to keep it warm and it never failed. The motor died and I replaced it with an 8HP Briggs. That was about 10 years ago. It still runs fine. It also has the original tires on it. So, I curious as to why your current machine goes through so many batteries, tires, etc...

 

[MossRoad]

By looking at the chart for the engine specs you quoted and plugging in the numbers for the diesel...

Torque = (HP * 5252)/ RPM

T = (20 * 5252)/ 3600

T = 29.2 ft pounds of torque

The gasser is rated for 7+ more ft pounds of torque when both engines are run at 3600 RPM. At that RPM you will have less power than the gasser.

 

[MossRoad]

I will have to say, though, that there is some argument as to how the engines are rated, who does the ratings, etc... to come up with their figures. It will still be an interesting swap.

 

[Soundguy]

In the end.. it's your machine and you get to do whatever you want with it.

Worst case it will be an interesting conversation piece down the road.

One of the tractor clubs i belong to there is this old guy with a BF-Avery that has been re-powered with a lawmower engine.. he did up the belt /clutches and all... the irony is that it probably has more hp than when new!.. even if it is an ugly looking mut.. he also added a 3pt hitch using a pulley system and a 12v winch!

soundguy

Ok guys, looks like I have a project now. I've acquired an engine and once the weather improves a bit, I'll start on it. It will probably be a couple of months before it's complete but I'll document my experience in doing so for those who would be interested.

I want to thank everyone who contributed their input.

I've attached 3 files: The specs on the donor engine, the specs on the current engine, and an image of the guinea pig tractor.

I know some of you think that this is a waste of time or effort but if it works out well, I will consider it a success. I'm actually very fond of this tractor. This being the reason I'm willing to invest the time/work into the swap. Sears does make some very inexpensive tractors, this was not one of them. This is a HST model purchased in 1998 for around $3200. It was their best at the time and is part of their Garden Tractor series with transaxle rated for ground engaging work. The mower deck is a 3 blade system and fairly heavy guage (comparatively speaking, 10 or 11 guage, I believe). Anyhow, I no longer require it to do anything but mow the field so as long as it has enough power to do that, and do it reliably, I'm happy with my time/money investment.

Mossroad: I know exactly what you mean by buying a new lawn tractor rather than dealing with the swap. But I've been there, done that. Had Murray lawn tractor, became unreliable, tired of changing batteries, tired of tires going flat, tired of rebuilding carburetor, etc. So, bought new Craftsman tractor. Old Murray still sitting in the field (10 years now). Result, new tractor needs new battery every year (fixed by modifying battery tray to accept CAR sized Optima battery), tires go flat every year and slips off rim (fixed by installing new Chev Ag type tires, much beefier and never lost a sip of air since). Now, engine is starting to require annual carb rebuilds, etc... No, I've no great desire to have another one of these in my field. When my toaster goes out, I'll toss that and buy another. But the current tractor deserves a little more patience....

 

[Superduper]

Found this on Kohler's website regarding their gas engines and their ratings:

* Horsepower ratings exceed Society of Automotive Engineers Small Engine Test Code J1940. Actual engine horsepower is lower and affected by, but not limited to, accessories (air cleaner, exhaust, charging, cooling, fuel pump, etc.), application, engine speed and ambient operating conditions (temperature, humidity and altitude). For more information, contact Kohler Co. Engine Engineering. Kohler reserves the right to change product specifications, designs and equipment without notice and without incurring obligation.​

This actually makes the engines even more equal in terms of horsepower. The Yanmar spec chart actually rates their engines in gross as well as net HP. Since Kohler does not provide data on the net output, suffice to say that the air cleaner, cooling fan, exhaust and alternator should have a meaningful but negative effect on the HP. I'm more excited now.​

 

[IXLR8]

As somebody that put a Subaru engine in his airplane and then flew it cross country, I am interested to see how this turns out. Please keep us posted.. lots of pics too.

 

[Blackbird_BX]

Looks like you're going to have your hands full for awhile. I look forward to reading about your progress.

I take it that the old gasser is air cooled. Did you order a radiator for the diesel?