OK, decision time: 28 or 35

[marrt]

I called Terry and my engine is shot. Less than 500 hours.

So, go with a 28HP EFI (really, a 25HP at 3600 RPMs) or upgrade to a bad boy 35HP Robin? Frankly, I'm a little scared of the 35...BUT...I see a lot of advantages as well. I think this should be a fairly safe upgrade. I'll be installed a supplemental fan with any upgrade.

Thoughts?

Tom

 

[KMA]

Personally, I wouldn't put more HP in the PT425 tub. I don't think there are enough "band aid" fixes to address the inherent heat related issues. If I do it again, the next engine will be liquid cooled with the radiator mounted external to the tub. I went with the EH72FI. Good luck!

 

[Frank Sorbello]

Kevin, do ou know what liquid cooled engine you would go with? I have often thought of finding one that would fit.

Tom, Did Terry say how much bigger the 35hp would be size wise? and are both EFI? Good luck in what ever you choose to do.

Frank

 

[Gravy]

I vote 35. Mine is working well with no supplemental fans or bandaids. I haven't done any scientific temperature testing, but it hasn't vapor-locked like the EH72 did. I'm assuming that it stays cool enough because it's a 40hp design tuned down to 35hp instead of a 25hp design cranked up to 28. It also starts way better in cold weather.

 

[Marks481]

Liquid cooling would be nice, but I don't think you will be able to shoe-horn it in without welding up a 6" tub extension. I have toyed with that idea several times, and the dimensions don't seem to stack up.

If you look back in the archives here, there is of course scarg'se Kawasaki 29HP liquid cooled conversion. But that didn't come close to fitting... he ended up raising the height of the hood by about a foot and strapping a gas tank on the back.

http://www.tractorbynet.com/forums/power-trac/112869-2004-model-pt-422-modified.html

Maybe it is time to go play around with Solid Works...

 

[MossRoad]

If the footprint is the same and the shaft sizes are the same and you won't have to re-engineer a bunch of stuff, I'd go with the higher HP. The motor won't have to work as hard, but that just means you might push it more?

In all seriousness, when I look at any piece of equipment, car, truck, boat, tractor, lawnmower, whatever, I look for the size model I want, then get the largest HP engine that's available in that size frame.

 

[MossRoad]

Liquid cooling would be nice, but I don't think you will be able to shoe-horn it in without welding up a 6" tub extension. I have toyed with that idea several times, and the dimensions don't seem to stack up.

If you look back in the archives here, there is of course scarg'se Kawasaki 29HP liquid cooled conversion. But that didn't come close to fitting... he ended up raising the height of the hood by about a foot and strapping a gas tank on the back.

http://www.tractorbynet.com/forums/power-trac/112869-2004-model-pt-422-modified.html

Maybe it is time to go play around with Solid Works...

Yes, I believe your are correct. There just isn't enough room for a liquid cooling system in the existing tub. You have to either go UP or BACK.

 

[Frank Sorbello]

Is the footprint of the 35hp engine much larger than the 28hp?

 

[marrt]

Frank,

If I remember right, Gravy said the 35 is only about half an inch longer. I assume that doesn't include the debris shield. Apparently, the 35 has some type of rotating debris shield that keeps junk out of the fan. Grady also mentioned the engine was actually a bit narrower than the 25 which could help a lot with cooling.

I was leaning toward the 28 but, after the responses here, I may go for the 35. It's not much more expensive and it's not a Subaru (it's a re-badged Generac). Whatever I do, I'll try to document it with lots of pictures. I already have new wheel motors on the way and a suspension seat in the garage along with some new LED lights. So, might as well do everything at once.

Tom

 

[ponytug]

Not that I know diddly, but it seems like it worked well for gravy. Besides, it is your nickel, but if it is close, I'd go with the 35, for a slightly different reason. The Generacs have been designed and built to be in confined spaces, so it probably has an edge on dumping heat.

If you do, I would be interested to hear whether you end up using it at half throttle, or wide open. My bet would be that you can get the RPMs up, but that the fuel consumption isn't going to be much different than your current machine.

Sorry that you have to replace the engine. I hope that the next one treats you better.

All the best,

Peter