First of all I'd like to thank you guys for your help and input [8D]. !!

The boat is actually a 48 inch screwdriver... built to scale from plans by P. Simmons.
I got it from a friend who had built it ... just perfectly... still needs painting. (plywood construction). see photos.

He also ave me 2 nitro engines ... Magnum marine engines ... a .60 and a .91 XL
That's why I'm sticking to nitro engines since I have them.
Besides, Homelite & Zenoah gas engines for RC are not available here... I'd have to go research weeders & chainsaw spare parts dealers & modify for application.

Nitro fuel is relatively cheap here. I use it on my HPI savage truck, and other .20 OS powered off shore boat, with great results.

I'm definitely not looking to brake the sound barrier (LOL) ... nor get to the 100 mph mark.

I just want a thrilling, water biting boat... and get the best with what I have.

What prop would you recommend for use with either engine?