Yeah, but the OS are nice motors, I have one in my heli a .32, runs sooooooo nicely. plus a marine specific engine will have water cooling, not totally neccesary in a rigger due to the open design but most generally tend to run water cooled engines, more consistent temps despite air temp, how your driving it and what not, plus adding a water pickup is so easy, some fuel line and a brass tube to make the thing, plus if you eventually get an inboard and want your engine in it then you will have an engine that is compatible, cuase an inboard does need cooling...I'd go the OS marine route, not the cheapest but it wont dissapoint.