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post #1 of 34 Old 09-12-2019, 03:34 PM Thread Starter
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Various horsepower on lawn/tractors?

I bought a Craftsman lawn mower recently. It has a Craftsman (Tecumseh) 13.5 engine. I've noticed at looking for parts, etc, that there are so many different versions of HP in mowers these days: 10HP/ 8HP/ 10.5, for basically the same "mower".

Why is there so much different HP's on basically on the same mower?

Back in the old days (1970), my cousin had a Cub Cadet tractor with a 7HP engine. That seems to work just fine.

Just curious.
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post #2 of 34 Old 09-12-2019, 03:58 PM
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Re: Various horsepower on lawn/tractors?

More hp in newer tractors needed for:
  1. Hydrostatic transaxle
  2. Hydraulic deck lift
  3. Hydraulic 3PH
  4. Hydraulic loader/blade
  5. Bigger deck
  6. Higher capacity deck
  7. Power steering
  8. Lights

In some cases, the rating of hp has changed too.

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post #3 of 34 Old 09-12-2019, 04:12 PM Thread Starter
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Re: Various horsepower on lawn/tractors?

But these are riding mowers, not tractors to push snow, etc. Just "Plain old mowers". It was just confusing.

My Craftsman has 13.5 HP, but a comparable Toro has only 8HP. Seems odd to me.
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post #4 of 34 Old 09-12-2019, 04:22 PM
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Re: Various horsepower on lawn/tractors?

Yep. My dad’s first and only lawn tractor was a 10 hp Allis Chalmers, sorry I don’t remember the deck width (1966).

Hydrostatic transmissions takes 3-5 hp. A widow friend had several 42” lawn tractors ranging from 15 hp, 19 hp, 20 hp. 48” decks require 3-5 hp more. My Husqvarna 52” has a 27 hp. Bigger decks require even more and anything with a PTO even more. Each has to do with the end usage market.

JD 2014 X738; 25.5 hp; HDAP tires; 54” deck auto-connect; hyd. angle quick hitch;
adapted to Cyclone Rake Commander Pro; 54” snowblower; front PTO kit; LP41114 Enclosure; LED lighting; 54” blade; 125# mounted spreader; 10P cart

Scotts 2002 L17.542 17.5 hp; 42" w/bagger
Sold Husqvarna 2010 GTH27V52LS w/52" fab deck
Craftsman DLT2000, 48”
Ariens ST824 snowblower
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post #5 of 34 Old 09-12-2019, 05:47 PM
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Re: Various horsepower on lawn/tractors?

Horsepower above the needs of the hydro are for powered implements. Many LTs (riding mowers) are also used for optional snow throwers/blowers which demand a lot more horsepower than a mower deck of similar cutting pass width, depending on quantity and type of snow.

Hydros typically use 20% more horsepower than they are outputting. Considering that the entry level hydros used in LTs have a max horsepower throughput to the rear tires of less than 3 hp, that doesn't come out to much of a drain on the engine.

It takes torque to move a tractor more than horsepower. Even the large heavy GTs rarely use more than 8 hp for pushing/pulling, but they need torque up the ying-yang to do it under heavy load conditions, and a big hydro produces that all out of proportion compared to engine capability, especially for FEL or dozer type work. The small hydros in LTs don't have anywhere near the torque capability of the larger hydros. I've used my 20 hp GT with the throttle just off idle to push a 2200 lb log, end on, across my lawn with no problem. (The throttle cable was seized.) A feat that a light LT with a light hydro cannot imitate, even at WOT. The loader on that tractor had no problem lifting one end of that log 3' in the air at the same, just above idle, throttle setting.

I ran a 12 hp MF12H GT with a loader and rarely set the throttle at more than 2/3.

In the list composed by RT3360 above, items 2,3,4,7, and 8 can be discounted as not being used for more than 2-3 seconds at a time, or are of limited loads on the engine. The charge pump used for powering hydraulic lifts and power steering uses about 1.5 hp, but only when doing max performance work such as lifting a mower or other implement. P/S only uses horsepower when the wheel is turned, and not much even then. Lights on todays tractors rarely require more than 0.03 hp to power. A 20 amp alternator uses about 1/3 hp with a 100% load.

Bundle it all together and maybe 3 engine horsepower, at specific times, are used by an LT to travel across a level lawn. Add a 10° slope to the travel load, and the horsepower demand rises to about 5 hp for travel. The rest of the horsepower is for the mower.

You buy a tractor with an engine rated for the expected horsepower demand of the implement, not for pushing or pulling. For that, you need a bigger transmission and a heavier tractor. Engine size is not as critical, and usually a lot less.

Bob

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post #6 of 34 Old 09-12-2019, 07:12 PM
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Re: Various horsepower on lawn/tractors?

My old 4 hp Wheel horse will out pull all the cheap junk....


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post #7 of 34 Old 09-12-2019, 07:48 PM
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Re: Various horsepower on lawn/tractors?

I've got an old mostly original, running 1967 Cub Cadet 102 with manual trans and 10hp Kohler. That small tractor was designed to pull a plow, 42" deck with 3 blades, snow blade, cultivator, sickle mower and other various implements, but on smaller scale as much larger farm tractors. It had a driveline from engine to rear axle that was a cut down version of a Farmall Cub Cadet rear axle. It didn't mow quickly, but mowing wasn't all it was meant to do.

Now, I move up to my semi-zero turn 1990 Kut Kwick front deck mower and while it can't do anything but mow(no accessories), it does it with force and speed with only a 20hp ONAN engine pushing a 60" 3-blade deck that can mow down, up to 1-1/2" saplings while pushing a rear steered, tricycle wheeled framework, weighs upwards of 1200#s and is 11 feet long. It's basically a farm brush hog(finish mower) with a seat/motor/steering wheel. It costs a lot more though, but at least I can weld on it if it breaks.

Todays mowers aren't like the heavier slower mowers of the past. They are built with pulleys that give an owner an extra speed of 1-2 mph, larger decks that cut, bag, vacuum clippings, but can't pull a trailer that weighs more than 200#s or you blow out the transaxle it seems. So you get a larger motor to cut wet grass, faster speeds, hydro trans because all these things require extra engine power, but mowers that don't last as long. But hey, it has 27hp to carry that 300# rider.

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post #8 of 34 Old 09-12-2019, 09:23 PM
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Re: Various horsepower on lawn/tractors?

If anyone here believes HP figures I've got a bridge I might be willing to let go at a good price (just for you) I might even throw in a noble statue, or two.
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post #9 of 34 Old 09-12-2019, 10:07 PM
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Re: Various horsepower on lawn/tractors?

Quote:
Originally Posted by TUDOR View Post
Horsepower above the needs of the hydro are for powered implements. Many LTs (riding mowers) are also used for optional snow throwers/blowers which demand a lot more horsepower than a mower deck of similar cutting pass width, depending on quantity and type of snow.

Hydros typically use 20% more horsepower than they are outputting. Considering that the entry level hydros used in LTs have a max horsepower throughput to the rear tires of less than 3 hp, that doesn't come out to much of a drain on the engine.

It takes torque to move a tractor more than horsepower. Even the large heavy GTs rarely use more than 8 hp for pushing/pulling, but they need torque up the ying-yang to do it under heavy load conditions, and a big hydro produces that all out of proportion compared to engine capability, especially for FEL or dozer type work. The small hydros in LTs don't have anywhere near the torque capability of the larger hydros. I've used my 20 hp GT with the throttle just off idle to push a 2200 lb log, end on, across my lawn with no problem. (The throttle cable was seized.) A feat that a light LT with a light hydro cannot imitate, even at WOT. The loader on that tractor had no problem lifting one end of that log 3' in the air at the same, just above idle, throttle setting.

I ran a 12 hp MF12H GT with a loader and rarely set the throttle at more than 2/3.

In the list composed by RT3360 above, items 2,3,4,7, and 8 can be discounted as not being used for more than 2-3 seconds at a time, or are of limited loads on the engine. The charge pump used for powering hydraulic lifts and power steering uses about 1.5 hp, but only when doing max performance work such as lifting a mower or other implement. P/S only uses horsepower when the wheel is turned, and not much even then. Lights on todays tractors rarely require more than 0.03 hp to power. A 20 amp alternator uses about 1/3 hp with a 100% load.

Bundle it all together and maybe 3 engine horsepower, at specific times, are used by an LT to travel across a level lawn. Add a 10° slope to the travel load, and the horsepower demand rises to about 5 hp for travel. The rest of the horsepower is for the mower.

You buy a tractor with an engine rated for the expected horsepower demand of the implement, not for pushing or pulling. For that, you need a bigger transmission and a heavier tractor. Engine size is not as critical, and usually a lot less.
You are touching on a subject that I have often pondered...why are all the older GTs small HP (8-14) horizontal shaft engines ...that seem more capable of a new 16-23 HP vertical shaft engines....or is it just MY perception?
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post #10 of 34 Old 09-13-2019, 02:07 AM
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Re: Various horsepower on lawn/tractors?

Well, we haven't been down this particular trail for several years, so I guess that it's time to thrash it out for the benefit of the more recent members.

There are many reasons, all open to discussion as to whether they are fact based, or opinion based on personal usage by the more senior members which will often hold the same prestige as fact. I'll mention a few to get this started, but I yield to those whose expertise is superior to mine, which is just about everyone.

- #1 is the fact that the method of calculating an engine's horsepower has changed several times since the '60s and '70s, as well as the legal aspects of how many horsepower are allowed in a LT/GT to remain within those classifications. A case in point, name the make/model that was built prior to 1980 that came with a 20 hp engine. There are lots that came with 19.9 hp engines.

- Older GTs usually came with cast iron engines. Newer models rarely, if ever have cast iron blocks. They may have cast iron sleeves, but the blocks are aluminum.

- Old technology relied more on a brute force approach to getting the job done, whether pulling logs, or ramming air into the combustion chamber. The new technology uses computer modeling to get the same effect out of lighter and/or smaller components for feeding the engine its fuel/air allotment.

- In days gone by, a 2 hp increase often called for an increase in engine displacement, or a whole new block to allow that increase. Today, fuel induction (not necessarily fuel injection) changes will often allow 2 or even 3, two horsepower increment changes to the same block with no other changes required, much as the various horsepower Chevy 327s of the '60s that had nothing different than an intake manifold and carb change to go from 195 hp to 235+ hp.

- The old engines had splash lubrication which required owner maintenance dedication to achieve a long service life. The newer engines have pressurized and filtered lubrication delivery that is less of a maintenance hassle.

These are but a few of the talking points. Bottom line, compare apples to apples. Use the current methods of horsepower calculation and you may find that the old engines were substantially under rated. They were certainly durable with proper maintenance. Keep in mind that lighter in weight scores positive points in hot air balloons, but it doesn't keep the tires in firm contact with the ground when pulling mom's car out of the ditch.

Okay, I'm done! Have at it gents.

Bob

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Last edited by TUDOR; 09-13-2019 at 02:20 AM.
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post #11 of 34 Old 09-13-2019, 02:19 AM
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Re: Various horsepower on lawn/tractors?

HP = Horse Poop.

Where it makes a difference is at the high rpm, one will have to be in that sweet spot of the power band. Most of us don't rev that high, and if we do, you need to be tuned perfectly to see what the rated HP really is. And tow a fuel tank around, I suggest the Flo n Go 14, it is orange and matches the tractor.

Just get on the **** tractor, drink your beer and cut the grass.

Now, if you add fuel injection...



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post #12 of 34 Old 09-13-2019, 06:51 AM
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Re: Various horsepower on lawn/tractors?

All good points listed above and I agree with all.
But a few weren't mentioned.
Bigger is better.
Horse power sells.
Just our society today. Who the heck wants a puny 100 h.p. pick-up truck when you get 450 and sit 4 feet off the ground.

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post #13 of 34 Old 09-14-2019, 04:14 AM
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Re: Various horsepower on lawn/tractors?

Quote:
Originally Posted by 4Get GTO View Post
All good points listed above and I agree with all.
But a few weren't mentioned.
Bigger is better.
Horse power sells.
Just our society today. Who the heck wants a puny 100 h.p. pick-up truck when you get 450 and sit 4 feet off the ground.
Even so, the moose will still join you on the front seat when you hit him.

Bob

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post #14 of 34 Old 09-14-2019, 06:48 AM
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Re: Various horsepower on lawn/tractors?

Per Kohler on how they rate their HP on today's engines:

Power (hp) and Torque (ft lbs) specifications for Kohler general purpose engines are rated pursuant to Society of Automotive Engineers (SAE) J1940 based on gross output testing performed according to SAE J1995 without the air cleaner and muffler. Actual engine power and torque are lower and affected by accessories (air cleaner, exhaust, charging, cooling, fuel pump, etc.), application, engine speed, ambient operating conditions (temperature, humidity and altitude) and other factors. This J1940 / J1995 rating provides consistent measurement to customers who may want to control the intake and exhaust features of the engine.

https://kohlerpower.com/en/engines/p...pro-ch23-ch680

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post #15 of 34 Old 09-14-2019, 09:10 AM
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Re: Various horsepower on lawn/tractors?

Tudor pretty much nailed it. Changing stuff like a carb supplier or configuration gets another rating. I'm sure the MTD purchasing department gets sales calls from every engine manufacturer, at least once a month to introduce yet another new and improved engine..... Sort of like "No Oil Change" models....you get it.

Its Saturday, model X's HP rating must now be 13.9 instead of 12.8.

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