View Full Version : Question,engine vs decksize

03-22-2004, 08:25 PM
am looking at new mowers and found a style I like it had a 54 inch deck and 20hp engine. a friend of mine told me that was not enough engine for the deck size. I don't undrestand because the engine should have nothing to do with the deck. I have seen this a lot on lawnsite to, can you all shed some light on this please? thanks Bill

03-22-2004, 08:56 PM
The bigger the deck, the more grass it takes in and power needed to cut it. I've used 20hp with 52" decks for some time and works very well. No problem getting through tall grass and no apparent strain on the engine. Put a 60" deck with it and it may be different. I think you will be fine with it.

gene gls
03-22-2004, 09:11 PM
It dependeds on the brand of mower and how it is set up. Mid mounts need more power than out front deck units.


03-22-2004, 09:24 PM
wb or rider? I'd say it has enough power.

03-22-2004, 09:27 PM
Originally posted by gene gls
It dependeds on the brand of mower and how it is set up. Mid mounts need more power than out front deck units.


Why is that? I mean differnt power requirements for the two types.

03-22-2004, 09:34 PM
Costcutter THE DECk has everything to do with the engine. A hydro machine needs more HP than a gear or belt drive machine.

03-22-2004, 10:55 PM
Personally, I'd say it is underpowered. Not sure, but I think the rule of thumb is 5 hp for each foot of deck.

Albemarle Lawn
03-22-2004, 11:05 PM
I have a John Deere HD75 with the 54" deck and a one-cylinder Kawasaki 17HP motor. Plenty of power.

Any more than 20 HP and you are wasting fuel for power you might only need 10% or less of the time.


03-22-2004, 11:26 PM
The design of the deck makes all the difference. The older Toro decks that were shallow would need more hp than the new deeper decks. I had a 48 inch Hustler Shortcut w/17hp Kawi and it was underpowered for Florida lawns. True I didn't need more power all the time, but when I did need more power it was very frustrating and really slowed me down.

03-23-2004, 01:35 AM
My walkbehinds are 48" and 15 to 17 HP....Iwant more power and believe you can never have enough....If you choose a
bigger engine it won't necessarily use alot more gas all the time (see threads regarding engine size and pick up trucks....alot of times a bigger engine loafing along will be more economical than a straining smaller engine...this doesn;t even take into consideration the longevity differences between a loafing engine vs a straining engine.....I'm retrofitting a 23 Kaw on my 48"

03-23-2004, 08:14 AM
What you really have to consider is Torque ratings. Torque is what does the work.

Higher HP will usually give you higher torque ratings in gasoline engines but you have to compare them. The deck does have alot to do with the engine as does everything that you attatch to the output shaft. You may not notice it until extreme conditions arise. You may never need it but when you do, it has to be there.
I have owned a 25HP and a 26HP Kohler engine. You would think that the 26 would use a little more fuel. That is not the case. In fact the 26 uses about 15% less fuel than the 25 and it has more torque. The difference is fuel injection. As a matter of fact if you are looking at the Kohler 20hp for your mower, it uses about as much fuel as the 26EFI and has a lot more torque. The price is higher initially but you are getting much more for the money. Here are the specs

High Performance Kohler CH26 Electronic Fuel Injection Engine, 725CC (44 cu. in.) displacement, 26-HP @ 3600 RPM, Max Torque = 41.6 ft-lbs @ 2200 RPM

Kohler CH20, 2 cyl 624CC (38.1 cu. in.) 20hp @ 3600, Max. Torque =32ft-lbs @ 2500

More torque at lower rpms, more HP and about equal fuel consumption. Good Luck.