I'll use this for home use, mowing about 4-5 acres per week. The Tank I am looking at is the M48 with the welded deck. I noticed in one of the brochures that the 19, 23, and 25 hp Kawasaki engines all show the same displacement (41.2 cu in) and compression ratio (8.1:1). What is different that gives those different horsepower and torque? Do they have different carburetors?