Read here[X(]: the people at PAW once put a huge 18-6 prop on a PAW 35 engine and started it. It could turn only 3500 rpm, but it ran for <five> hours straight with no damage to the engine! The test was stopped just because the people wanted to go home.
The text are from the link:
http://www.antiquemodeler.org/Engines/diesels.htm
Jens Eirik