While I use MX2t in everything and I find it runs better in my air cooled lawn eqpt. I know that the lawn stuff is light duty. The engines make very little HP and really do not rev that high. With that in mind, boat oil will lubricate the engine OK.
However the oil is not designed for the high temps of air cooled engines. So, excessive deposits or spooge out the exhaust can be a problem in the long run. Also, piston ring sticking can occur with the wrong oils. Synthetic oils are better at preventing ring sticking.
Chris