Min PTO HP for 7.5' finish mower

GManBart · Jun 21, 2013

I'm considering getting a dedicated mowing tractor to save myself some time, and I'm trying to figure out how small I can go (I already have a ZT for the tight areas around my house/fence). I picked up a super clean 7.5' finish mower (Sitrex SM230) at auction and have been running it behind my LS, which runs it like it's not even there. I'm in the middle of a long project to clear land, demolish buildings, backfill old foundations etc, etc, so I'm using the LS to move dirt, serve as a 4WD forklift, etc. Having the mower deck on it isn't convenient (or enough counterweight for moving dirt), so I wind up swapping for the counterweight back and forth every other time I go to do something. I have enough land that I need to mow pretty frequently, and would like to be able to leave the mower deck on a tractor, ready to mow, whenever I have time.

What do you think the minimum PTO HP should be for a deck that wide? It's also nearly 700lbs, so I can't go too small or it will be cumbersome. I was sort of thinking it might take close to 30hp at the PTO....thoughts?

Anybody run a finish mower this big with a smaller tractor?

J_J · Jun 21, 2013

The general rule is about 5 HP per ft.

GManBart · Jun 21, 2013

J_J said:
The general rule is about 5 HP per ft.

That's really for brush cutters, not finish mowers. My LS only has 38hp at the PTO if my memory is correct, and it isn't working hard to run this deck.

J_J · Jun 21, 2013

Depends on what you are cutting, lawn or field.

Look at the RDC72, requires about 25 - 35 and also look at the other finish mowers.

Finish Mowers

rbargeron · Jun 21, 2013

GManBart said:
........ I was sort of thinking it might take close to 30hp at the PTO....thoughts? Anybody run a finish mower this big with a smaller tractor?

I can run a 90" finish mower on my smaller tractor - around 29 pto hp. It has it's hands full going uphill in tall grass - but by going slower or tasking less of a bite it will manage. 40 pto hp is a better match for a 90" cut but if you don't let the crop get too heavy 30 pto hp will get the job done.

Turbys_1700 · Jun 21, 2013

I ran a 5' Land Pride finish mower 14 years with a YM1700 Yanmar...
That Yanmar is rated at 17 HP at the PTO and it ran the mower just fine...
I now run a 6' Woods PRD 7200 with a New Holland 1720 that is rated at 23.5 HP at the PTO and it runs it just fine...
I will say though that this is the absolute minimum HP per foot cut that I could recommend...
The Yanmar Land Pride combo was running @ 3.4 HP per foot cut and the New Holland Woods combo is running @ 3.9 HP per foot cut...
I can tell you that the 6' Woods PRD takes considerable more power to run than the 5' Land Pride...
The difference seems more than 20% due to the extra weight of the Woods...
If I was looking at a 7' or 8' RFM I would be looking @ minimum of 28 HP for the 7' and 32 HP for the 8'...

J_J · Jun 21, 2013

The Woods site says your 90 requires about.

Tractor horsepower 45 - 75 hp

Think of it as work, and work = HP and just turning the blades does not take much HP, but get into some tough grass and the engine will start to lug based on the load, using what HP is available.

We are talking about a useful match of HP and width of cut and type of cut.

GManBart · Jun 21, 2013

J_J said:
Depends on what you are cutting, lawn or field.

Look at the RDC72, requires about 25 - 35 and also look at the other finish mowers.

Finish Mowers

Good point. I have 5' and 6' brush cutters to go over the heavy stuff. The plan is to only use the finish mower for normally grassy areas, and the brush cutters for everything else. Ideally, I'd like to be able to run the 6' brush cutter on the smaller machine as well (which still puts me around 30hp at the PTO), but it's not critical.

GManBart · Jun 21, 2013

rbargeron said:
I can run a 90" finish mower on my smaller tractor - around 29 pto hp. It has it's hands full going uphill in tall grass - but by going slower or tasking less of a bite it will manage. 40 pto hp is a better match for a 90" cut but if you don't let the crop get too heavy 30 pto hp will get the job done.

Thanks...that makes sense, and was pretty much what I was thinking. I don't have any steep hills, and if I can mow for a while, and it gets really tall, I can always run the brush cutter first, or use the bigger tractor. R,

GManBart · Jun 21, 2013

Turbys_1700 said:
I can tell you that the 6' Woods PRD takes considerable more power to run than the 5' Land Pride...
The difference seems more than 20% due to the extra weight of the Woods...
If I was looking at a 7' or 8' RFM I would be looking @ minimum of 28 HP for the 7' and 32 HP for the 8'...

Thanks...my Sitrex is pretty heavy, at almost 700lbs, so I was factoring that in as well. Looks like your numbers are working out pretty much the way I was thinking...ballpark of 30hp at the PTO.

joecooler · Jul 29, 2013

GManBart said:
Thanks...my Sitrex is pretty heavy, at almost 700lbs, so I was factoring that in as well. Looks like your numbers are working out pretty much the way I was thinking...ballpark of 30hp at the PTO.

This is a 96" LMC (Sovema EMH-2) on my restored JD 300. 43 gas Hp. The mower is way heavy and over 800lbs. Its really a near perfect match. I end up running a little hot on the PTO to get a nicer cut, but the power is just right, even enough for thick 2 foot grass (going slowly). I would go no less than 35 HP for the tractor to ensure you have adequate surge power.

GManBart · Jul 29, 2013

joecooler said:
View attachment 329479 View attachment 329480

This is a 96" LMC (Sovema EMH-2) on my restored JD 300. 43 gas Hp. The mower is way heavy and over 800lbs. Its really a near perfect match. I end up running a little hot on the PTO to get a nicer cut, but the power is just right, even enough for thick 2 foot grass (going slowly). I would go no less than 35 HP for the tractor to ensure you have adequate surge power.

Nice mowing rig!

mikehaugen · Jul 29, 2013

I have a woods rm90 that I ran with my jd1070 (38hp, 35pto). It did just fine. That is a heavier mower too, around 900# I think. If you are just cutting regular grass, not too long, I would say less could do it. 30 hp would probably be okay, but you need to be religious about not letting it get too long.

My mower is actually pretty heavy duty and I used it cutting some 4'-5' grass as well as some other 'hogging chores before I bought a woods rotary cutter. Had to go slow, but it did it.

Halftrack · Jul 29, 2013

I run a Sitrex 230 behind my TC 33D and haven't worked the engine hard yet. In wet heavy grass I think the mower protests louder than the tractor. I bought the mower used and have been very impressed with the quality of cut.

jenkinsph · Jul 29, 2013

joecooler, thats a very nice looking 300, good job on the restoration.

Turbys_1700 · Jul 30, 2013

joecooler said:
View attachment 329479 View attachment 329480

This is a 96" LMC (Sovema EMH-2) on my restored JD 300. 43 gas Hp. The mower is way heavy and over 800lbs. Its really a near perfect match. I end up running a little hot on the PTO to get a nicer cut, but the power is just right, even enough for thick 2 foot grass (going slowly). I would go no less than 35 HP for the tractor to ensure you have adequate surge power.

Nice tractor there Joe...
Did you do the restore or buy it that way???
Good looking rig...

Deerherd · Jul 30, 2013

If there was a "Tractor of the Month" here on TBN, I would nominate Joe's Ford. SWEET!

LD1 · Jul 30, 2013

Im a little late, but what did you decide.

I see you list a 8n, I would think it would work fine on it. Might have to slow down a tad, but do-able.

30hp seems about the right ballpark.

HP just allows you to cut faster/not bog down.

Heck, remember a few years ago before all this ZTR craze. It wasnt uncommon for a 12HP or 14HP riding tractor to be paired with a 48" deck.

By those numbers. you could run a 10' on 30hp with the same efficiency. Remember when mowing, HP = Speed. So your big tractor may allow you to mow a gear or two higher than a 25-30HP machine, but the smaller rig will still do it just fine.

GManBart · Jul 30, 2013

LD1 said:
Im a little late, but what did you decide.

I see you list a 8n, I would think it would work fine on it. Might have to slow down a tad, but do-able.

30hp seems about the right ballpark.

HP just allows you to cut faster/not bog down.

Heck, remember a few years ago before all this ZTR craze. It wasnt uncommon for a 12HP or 14HP riding tractor to be paired with a 48" deck.

By those numbers. you could run a 10' on 30hp with the same efficiency. Remember when mowing, HP = Speed. So your big tractor may allow you to mow a gear or two higher than a 25-30HP machine, but the smaller rig will still do it just fine.

Still haven't decided! The 8N is out...it struggles with the weight of a lighter brush hog, and the lack of a live PTO just slows me down too much. I've narrowed it down to looking for 30hp at the PTO, diesel, and live or independent PTO. Power steering would be a plus, and HST a major plus.

I looked at a MF 231 that's in really nice shape, and liked everything about it except for trying to get on or off...and I'm pretty nimble. I thought i was going to make an offer on a very clean Ford 961, but when we were supposed to meet, the seller couldn't get it started, and found the oil pan full of diesel. I've seen it once prior, but it had a dead battery, hence the planned second visit that didn't pan out. They still want to sell it (likely very cheap), but I'm pretty deep in projects right now. So, I'm still looking, and trying o come up with a smart plan. Last night I saw a sweet MF on Ebay that I may try to look at later this week...mich roomier station, and more power, for the same general size and weight. Decisions, decisions....