Max prop size

[coberg1]

Could I get some opinions from everyone on what the maximum sized three blade brass prop can be run by a 700bb motor without gearing, and also the max size prop that could be run with the same motor at 2.5/1 gearing? Without destroying the motor that is? I'm checking out what the best drive train for a 1/16th scale pt boat would be. I've gotten two opinions and two different recommendations so far so am looking for more views.
I'm leaning toward belt driven gearing because I've already some success with such a system. Hobby lobby claims .60 size gas engine equivalence with their 700bb belt drives which seems like plenty.
A scale prop for such a boat should be around three inch but the guy recommending direct drive is saying two inch.
Seems to me a three inch geared prop would offer a lot more power.

[CG Bob]

Could I get some opinions from everyone on what the maximum sized three blade brass prop can be run by a 700bb motor without gearing, A prop about 1.5 to 1.75 inches in diameter. The prop diameter shouldn't exceed the motor can diameter for a direct drive system.

the max size prop that could be run with the same motor at 2.5/1 gearing? With that gear ratio, you could run a prop up to 3.75 inch in diameter; the 3 inch prop would work better on the 2.5:1 gear ratio.