Can i put a 18 hp kohler in to replace a 12 hp kohler?

have cub cadet ih 124! engine ran out of sick days and called off dead!|||yes and no the shaft has to be the same size and it may or may not fit in the mower itself i put a 12hp BS into a 8 BS and it worked shaft was same size|||Yeah go for it!|||If the 18 hp is for a lawn tractor it will work just fine and should make a good trade. Just measure the shaft. The mounting pattern should be the same. Engines that are made for generators as an example have a tapered shaft. Not much good for lawn mowers.