Well, I’m sure a 10hp with wrist pin bearings would run fine on 50:1 with good oil. I prefer to adhere to the original recommendation to ensure the engine has a good margin of error for those situations that might result in scuffing/scoring, such as overheating, lousy fuel, lugging, etc. A nice 10hp is not easy to replace. I’m guessing the engine won’t get used much, so the added expense is negligible. When these engines are in good shape, and tuned properly, they rarely smoke, even with 24:1. The extra oil left behind in the crankcase will help minimize internal rusting during long periods of non use as well….