Kohler 23hp engine replaced the old 20hp. This is my favorite engine for price and performance. Quality greatly exceeds that of the 18hp Briggs, although the Briggs features a back-up recoil pull starter. The Kohler features hydraulic valve lifters, oil cooler, and an accelerator pump on the carburetor for quick throttle response. The 23hp Kohler is the top of the line Max II, available on the Max IV, and standard on the Buffalo Truck.
Recreatives has just added the largest ever liquid cooled engine, the 27hp Kawasaki, to the Max IV line up. Information is available on THIS page.