Ok -- lets see who runs what on a particular boat - and why you choose that prop - via ski , race , pleasure -
mine -- 11.5x14-three blade - why - was trying to cominsate for tall gears(29's) - boat 21 foot howard cruiser - with about 600 ponies 15 gears
11.25 x 15 prop, 18 gears and around 550HP in front of THM400. Props probably fine, still a bit tall on gear, boat is just a lake hot-rod.