I am in the process of fitting a new 25HP Yamaha High Thrust engine to replace a Tohatsu 20hp engine. Apart from the extra 5hp I am hoping for better push from the 12.25" prop comared to the 9" Tohatsu prop. Visually apart from the bigger diameter the Yamaha prop has a much bigger area, I suppose aided by the 2.42 gear ratio compared to the 2.17 Tohasu ratio.
So I am hopeful of this being a good upgrade ( aapart from a new engine to replace a seven year old one) and worth the work of modifying the cockpit engine cover and maybe the rudder connecting bar as the new engine is higher when tilted. I will report back on how it goes when fitted in May.