Motor looks identical but I see they have one rated at 21hp. Mines 19.5hp. Makes you wonder what they did differently for an extra 1 1/2hp ? Under the seat the first 6 numbers in the serial number is the date it was built. The fifth and sixth number is the year.
They've used Briggs a lot in these and guessing other manufacturers too and many different horsepower ratings. The other one I picked up has a 14hp single cylinder on it.
Not sure but I think it was Kohler who got a lawsuit against them a number of years ago for inflating horsepower numbers.
HP is irrelevant. LOL
For decades, Briggs would label engines 6HP when they were 6.5Hp and the other way around. They knew the performance and how to tweak the numbers. Then sell products on the Hp hype markup.
For example, different air filter sizes and baffle can raise or lower an engine by up to 1Hp. The same goes for the spark plug used.
Additional engine tweaking deals with the flywheel head and the magnetism to the coil. Lastly, it's the spring on the carburetor throttle, if the same carburetor is used.
Many of the tractor manufactures did/do the SAME THING. It go so bad, that the Nebraska NTTL stepped in decades ago to verify the hype or claims.
tractortestlab.unl.edu
Larson started all of this.
Built in 1919, to satisfy the needs of the Nebraska Tractor Law, our original building was designated as an historic site by the American Society of Agricultural Engineers. It now houses the
Larsen Tractor Test & Power Museum.
The Ag manufactures knew how to tweak fuel pumps with shims and change injectors on the engine, without needing to change the engine at all. LOL. Air filter throttling was another good method too. Choke the air intake, reduce the Hp. Biggest air filter and intake neck achieved the best Hp and performance curves.
With my Yanmar YM2610, I could change out the shims in the fuel pump, the injectors, taller fuel filter and larger air filter in the canister to match the YM4300 (JD1050) and boost to nearly 40Hp from 31Hp. People have done this and even added the IHI turbo, reaching 45Hp.
So yeah, you can mess with the marketing Hp numbers or mess with the engine air and fuel to get a higher Hp rating on the same engine.