Engine manufacturers don't recommend it.
I rather doubt that Ford and Lehman were calling American Marine in Singapore in 1966 and warning them not to overprop their engine.
Most boat engines in the kinds of boats we have were derived from truck, industrial, or agricultural engines. As such, I daresay they worked a hell of a lot harder at times than they do in our our toy boats.
The Ford Dorset diesel, which was designed to be a truck engine, proved a miserable failure at this because the high-rpm, high-heat, constantly varying loads that are experienced in over-the-road trucks were too much for it.
But it found a new lease on life as an industrial (cranes, pumps, generators) and agricultural (primarily combines) engine. As such it was not subjected to the high rpm and constantly changing high loads of truck service, but I suspect that while the loads were more constant they were probalby often more than what our slighly over-propped boats demand.