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Model # 10603

Internet # 202558330

Store SKU # 163267

20 in. Kohler Engine Push Gas Walk-Behind Lawn Mower

This item has been discontinued.
The Home Depot no longer carries this specific product.




Model # 10603

Internet # 202558330

Store SKU # 163267

The Lawn-Boy 20 in. Kohler Gas Walk-Behind Push Mower provides the power to cut through tough grass, but is still lightweight and maneuverable. The 1/4 in. cutting height range provides a lawn manicured to your wishes. The deep dome deck is designed for superior bagging and mulching performance.

  • 149 cc (6.5 gross torque) overhead valve engine is efficient and can power through the thickest of lawns
  • Lightweight and maneuverable push mower
  • 20 in. wide cutting deck is ideal for trimming around obstacles
  • 1/4 in. cutting height range provides the operator a perfect cut
  • Multi-notched blade cuts grass into fine clippings for a clean cut
  • Deep dome deck designed for superior mulching and bagging performance
  • 7 in. front and 8 in. rear wheels provide solid traction
  • One piece handle is rigid for repeated mowing usage
  • Operator bail clutch bar will stop the engine and blade within 3 seconds after release
  • Operator handle folds down for compact storage
  • All Lawn-Boy mowers are backed by a 3 -year tru start engine commitment, a 3-year Power Train warranty and 2 year-full product warranty
  • 3-in-1 ready mower mulch and bag comes standard, Side discharge chute is free upon product registration
  • Delivered to your door mostly assembled, simply attach the handle using basic instructions, no tools required
  • Note: product models may vary by store
  • Note: Product may vary by store

Info & Guides

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Assembled Depth (in.) 
57 in 
Assembled Height (in.) 
1 in 
Assembled Width (in.) 
21.25 in 
Blade Length (In.) 
20 in 
Mower Deck Width 
20 in 
Rear wheel size (in.) 
Size of Yard 
1/4 Acre or Less 
CA (CARB) Compliant 
Not CARB Compliant 
Cutting Options 
Cutting Width (in.) 
Engine Displacement (cc) 
Engine Make 
Bagger,Foldable handle,Tool-free adjustments 
Fuel Type 
Fuel tank capacity (gallons) 
Engine oil 
Lawn Mower Type 
Walk Behind 
Manual Push Mower Type 
Maximum cutting height (in.) 
Minimum cutting height (in.) 
Mulching Capability 
Number of Blades 
Oil capacity (oz.) 
Product Weight (lb.) 
70 lb 
Recommended oil 
Start Type 
Walk Behind Mower Type 
Manual Push 
Warranty / Certifications
Manufacturer Warranty 
2-year full 


Rated 2.7 out of 5 by 52 reviewers.
Rated 3.0 out of 5.0 by Doesn't bag wet clippings I live on the coast. If your grass is a bit wet (which it always is on the west coast) the bagger is virtually useless. It just gets clogged in the first few minutes. June 19, 2011
Rated 4.0 out of 5.0 by so far so good... In the late summer of 2010 I was eyeing the lawnboy 10640, the predecessor of the 10603. Unfortunately, it was sold out everywhere. In the spring of 2011 I learned the 10640, which offered a Briggs & Stratton 6.75 HP engine, was no longer being offered and had been replaced by the 10603 which featured a slighlty less powerful 6.5 HP Kohler engine. Figuring the change in engines was due to cost, I contacted Lawnboy who never really gave me a straight answer when they emailed me back. They said they needed an engine manufacturer that could produce a large volume of machines for their mowers. And Briggs couldn't? So I went back to my original theory and concluded that the real reason was cost. Anyway, I researched Kohler and seemed satisfied so I purchased the 10603, figuring a 0.25 drop in HP shouldn't make a huge difference. Anything that is 5 HP or greater is normally sufficient. I used to work in property maintenance/landscaping and all we used were Lawnboys and Toros so I figured I couldn't go wrong as they are both excellent brands. And so far so good...the 10603 started on the first pull as promised and the height settings are much easier to adjust than on older lawnboy models. I cut my 3" lawn down to 2" using the bag and the machine left no clippings behind. The manual suggests that you only tip the machine on it's side when the tank is empty. I tipped it over on it's side even though I still had some fuel in there (dipstick side down, air filter side up) to clean it out and there were no fuel leaks whatsoever. I also like the large fuel neck, makes it a lot easier to fill. I chose the recoil model without the transmission because I feel that the more components you have the more likely things are to break. I chose this model because I don't care about an ignition start system and I don't need a transmission because my lawn is flat. So the 10603 suits me just fine. However, if you live on a hill you might want to consider the 10604 which is the self-propelled version. However, one of the downsides of the 10603 is also mentioned in a review for the 10604, namely that when you remove the bag the grass clippings make a big mess because of the angle they use to clip the bag onto the machine. I haven't used the mulcher yet so I can't comment on that. Lawnboy also offers a side discharge attachment too but you have to order it (free of charge). The only other downside is that the deck is not aluminum but not a huge deal. And the flap at the rear is a little flimsy, I am thinking of getting a 3/4" bar and zip tying it to the flap to add some weight for better striping and to keep it from going under the deck. The manual states to empty all fuel before winter storage but won't this create moisture in the fuel line? I will probably just use fuel stabilizer. All in all, I am happy with this machine and would buy it again. May 12, 2011
Rated 4.0 out of 5.0 by Great little mower for a small lawn I have a small lawn on a level lot. I just need a basic gas mower that did the job and did not need self propulsion. I decided to go with this model as it was a great price point. All mowers I reviewed had SOME complaints about not starting so I went with the 2 year replacement plan and still walked out paying only 255. When I got home, I pulled it out of the box, tightened the 2 screws to engage the handle, added oil and gas, adjusted the wheel height, gave it a weak yank on the chord and was off mowing. Great power, the clippings were adequately mulched without any fussing and I was done in no time. What more could you want? July 22, 2012
Rated 5.0 out of 5.0 by New Mower I finally broke down and bought a new mower. I went with this LawnBoy after reading other sites. I had been using a Toro Recycler with the variable transmission, but really didn't need that style (I live on 1/5th of a acre, most of which is my house). I was looking for a good push mower that was light weight and a good overall product. This unit is really light and all you have to do is put oil and gas in and give it a pull. Fired right up with about a 3/4 pull the first time. Have only used is a couple of times, but so far so good. Had no idea, but apparently Lawn Boy is a Toro brand. Didn't find this out until I was reading the manual. So I hope the quality transfers over from Toro. I have had the Toro for about 15 years. April 11, 2011
Rated 5.0 out of 5.0 by Starts great I enjoyed the mower being ready right out of the box. All I had to do was pour in the gas and oil. I did not need to connect the handle or anything- a nice surprise. It starts on the first pull- another nice surprise. My last mower took three pulls to start. It is a little small being only 20" but I knew that when I ordered it. The size was outweighed by other factors that I liked- the manufacturer and the motor. It is still early in the mowing season but my new mower and I are starting out very well. I am quite happy with it. May 1, 2011
Rated 5.0 out of 5.0 by Great mower I actually found this one in a store. I did not need self propelled as my yard is only about 4500 square feet. I have used this twice and love the bag feature. My old mower did not have a bag and would leave clumps, it was 35 years old, what do you expect right? This one has a bag and it works well. Just make sure the chute is clear when you put the bag back on or it will just mulch and not go into the bag. Found this one out after it didn't bag a couple times. Starts on one pull every time so far. One other thing, make extra certain the oil cap is on securely before you start it. It popped off on me the first time starting it, but now it works fine, hasn't done it since. May 20, 2012
Rated 3.0 out of 5.0 by Good mower despite defect Ordered this mower online. Starts right up and works very good. The only problem I had was with one of the front adjustable wheels. One of them would NOT stay in position. The adjustable lever on that wheel was defective. It's the only thing that ruined the experience. You expect your product to arrive in flawless condition but when it doesn't, you're feelings about the product you purchased bother you. From the initial sale all the way to delivery. It's a shame. Nobody likes to purchase a product with a defect no matter how minor it is. Quality control needs improvement. June 5, 2011
Rated 4.0 out of 5.0 by Dependable mower I have owned this mower 3 years now. Change the oil and air filter twice each season. Starts on 3 or less pulls, usually on the first pull. The self-propelled feature is not quite as strong as I would prefer however. Overall I would rate this a good value. October 3, 2012
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