Enough Power for 5' Finish Mower?

[Teese]

I just dropped the backhoe off my nominal 20 hp B20 (first time it had ever been off) and tried to operate a 5' (FDR1560) Land Pride finish mower. I couldn't bring my RPMs over 1900, and any forward speed faster than a heel-to-toe drunk driving test quickly bogged it down to 1500 in a fast dive. The Land Pride manual recites a maximum hp (35) but doesn't specify a minimum ... is 13.5 PTO hp (per TractorData) enough, or am I missing some?

 

[North Idaho Wolfman]

Yes that mower is a bit much for your tractor, It's about the same specs as the newer 60" model and that calls for a min of 25 HP to run it.
You might be able to get away with a 48" it's min is 15HP.

 

[moondog933]

5 horsepower per foot of cutter is what my Kubota dealer uses as rule of thumb on implements.....I don`t see that 5` finisher bogging down your tractor that much. Is the tractor blowing smoke ? tranny in four low ? Does it bog your tractor down by just engaging the pto and mower lifted not cutting ? Brain storming here...

 

[kubotasam]

I use a 60" land pride behind my B7100. It has 16 hp with 13 (I think) to the pto. My tractor runs it just fine. When I cut the field behind the house sometimes the grass is 2 - 3 feet tall. That will bog down my tractor but normal lawn grass cutting 16 horse power is plenty.

 

[chim]

The B7500 I had would handle a Landpride 60" RFM fairly well. The PTO on it is rated at 2-1/2 horses more than a B20. Going uphill or through tall grass required slowing down. My Ford 1210 handles a 60" Caroni just fine, but couldn't handle the Landpride. They both cut 60" but the LP was much heavier.

I tried swapping the decks between them. The B7500 handled the Caroni deck as though it almost wasn't back there.

 

[hodge]

I use a 60" land pride behind my B7100. It has 16 hp with 13 (I think) to the pto. My tractor runs it just fine. When I cut the field behind the house sometimes the grass is 2 - 3 feet tall. That will bog down my tractor but normal lawn grass cutting 16 horse power is plenty.

I run a Woods RM59- a 5' finish mower- all day long with my B7100, also. I just mowed grass as high as the hood last week- I kept the deck up about 6 inches, took the stalks down, then lowered it on the second pass and kept chopping it up. Absolutely no lack of power, and that was a lot of material. I will post a photo- it was a yard at an ramshackle house that hasn't been mowed in 4 years. A 13 pto hp tractor can run a 60" finish mower, and I wouldn't do it if I was overloading or damaging my tractor.
You need to check a couple of things- do the deck spindles turn freely (if not, you may have bound up bearings or debris around the lower shafts), do the idler pulleys turn freely, is the mower set too low, etc. Your tractor should be able to pull it. It may not mow in thick, fine grass while keeping the RPM's way up, but it should power it satisfactorily.
I used to mow with a Wheelhorse 520H- a powerful Onan 20 hp tractor with a 48" deck. My 13 pto Kubota with a 59" finish mower will mow circles around it, at 3/4 throttle, on half or better the fuel. No lie or exageration.

The grass in that yard was deep enough that deer had been bedding down all over the yard, and you wouldn't have seen them until you walked up on them. I mowed it 4 times to get it down as it is in the photo (chopping it up again and again), and then brushcut the bank on the right up to the tree line. If you look closely at the photo, you can see the growth that we hadn't cleared yet on the right side of the house, and the brambles/trash growth at the end of the tall shrubbery on the left- that's part of the creekbank. The woman who owns it hires someone about every 4 years or so to come in and clean up all the undergrowth. We (two of us) spent 6 days there cleaning the yard and around the house, a section of woods, and about 500' of creek bank. I mowed the yard numerous times, then mowed the sides of the creek bank once cleared.
I say all of this to make a point- my B7100 runs a 59" finish mower with power to spare. I have never taxed it yet. Yours should be able to also run a 5' finish mower at some reasonable level.

 

[Teese]

The B20 is HST and it was in low range. The mower height shims were set to the highest cut possible (5"). Standing still and engaging the PTO I see a drop from 2500 rpm to 1600, then a climb back to 1900 or so. I cleaned, greased, oiled and sharpened the mower just 2 weeks ago, and while doing so was able to freely spin the blades by hand during removal for sharpening.
There is no visible smoke while the tractor is at speed with no load; it smoked visibly while laboring with the mower.
That help?

 

[hodge]

Which range are you putting the PTO in? You should not run it in the highest range. I don't know what your tractor has, but my B7100 has two, which I use the low. That is right for the blade speed and load.
Mess around with the PTO ranges, and see if there is a difference.

 

[Teese]

Hodge
I see what you mean, TractorData.com's B7100 page says it has a 3-speed PTO (514/786/1498) rated at 13 hp ... and its B20 page says I have a "live" 540 rated at 13.5, so it's a single speed with the "live" apparently meaning (haven't tried it yet) that I can change HST speed ranges with a partial clutch depression, then disengage the PTO upon a full clutch depression, thus permitting the mower, etc., to operate while I fiddle with other controls.

It's my understanding that the LandPride presumes a 540 rpm PTO, but I suspect my B20's doesn't get to that until about 2500 engine rpm.

 

[RDR]

I hope you aren't letting the clutch out to start the mower with the engine at 2500 rpm. If you are and do a lot of mowing, plan on putting a clutch in too soon. I beat the hell out of my 1st Leyland 154 diesel for 17 years and never adjusted the clutch.

If the engine isn't getting back to 2500 with the mower on with no load something is wrong. No smoke sort of rules out the air filter. A diesel will do strange things with a lack of fuel. Always check the simple thing first.

 

[Teese]

EPILOGUE
Despite the established rules of thumb contributors noted with respect to hp-to-width for mowers, I took the comments with others' experiences to heart and, while still following Craigslist to see if something tantalizing (and more powerful) would show, set out to systemically ensure that I was getting all the power I should.
I surmised from perusing the OTT forum that my problem was related to air, fuel or compression; air supply/filter seemed fine, so I sprang for a HF compression test kit (Holy cow! I walked out with it for $28 while I saw the identical kit online for triple that!) and headed out to the lot to do battle with the B20. I thought I'd first check fuel ... and when I serially cracked the injector connections, the engine nearly died on cylinders 2 & 3, but didn't change at all on cylinder 1 (furthest forward)--so no wonder I had a power problem! Closer checking revealed that at the injector pump end, the metal line's flare nut was still sealed to the line by the original factory paint, but the injector body below it was a bit less than hand tight as it entered the engine. After mulling "How in the world could that be?" entirely too long, I disassembled the line, reassembled everything at guestimated torques, and fired it up. Engine sounded smoother and ran the 60" Land Pride finish mower on my 1.5 acres with no problem!
There is a bit of relatively clear blowby (pushes my finger off the breather tube end after a few seconds), so the compression kit may still become useful to see what's what ... at least that's what I told my wife.
Thanks so much for the comments here (and all across OTT on related topics) that helped me so much to solve this one!

 

[Bluegill]

I hope you aren't letting the clutch out to start the mower with the engine at 2500 rpm. If you are and do a lot of mowing, plan on putting a clutch in too soon. I beat the hell out of my 1st Leyland 154 diesel for 17 years and never adjusted the clutch.

If the engine isn't getting back to 2500 with the mower on with no load something is wrong. No smoke sort of rules out the air filter. A diesel will do strange things with a lack of fuel. Always check the simple thing first.

Worth repeating! I start my mowers at idle and then throttle up.

The tractor in question should pull a 60" finish cut just fine.