There was a misconception here that you can get more power out of the Suzuki 2.5 outboard on a TI if you change the prop.
Remember power is torque times RPM. You get the maximum power with the highest torque possible at the highest RPM possible. The best prop for a particular craft for speed is one where full throttle gets the RPM to just under the maximum RPM at the speed the craft is running at. This is how you get the rated HP out of the outboard.
So if a particular prop gets the craft to peak speed and is slightly under peak RPM, you are getting the maximum power from the outboard. Change to lower pitch prop and the outboard rev limits with less torque resulting in less power. Change to a higher pitch prop and the higher torque wont allow the higher RPM also resulting in at best case the same HP (if the power curve is fairly flat). If the reduced RPM takes you lower on power curve.. you end up with less power.
Take a look at how the experts match a prop to a power boat. They will always set the pitch (for a particular prop) so that the outboard gets to its design peak RPM at full throttle. If RPM is too low, go to a lower pitch prop. If RPM is too high (limiting), go to a higher pitch prop.
The stock prop on the 2.5 does in fact run at just under rev limit at full speed on a TI. The stock prop is matched fairly well to deliver the full 2.5 hp when used on the TI..
This video is only test I have seen with the TI where the prop pitch was looked at and shows that the stock prop is about right.
https://www.youtube.com/watch?v=kNbpoeaCe80&t=1sIf someone does want to mess with the prop, please make sure you do a good controlled experiment where you measure peak speed with the stock prop, then the ONLY thing you change is the prop and measure speed again. As far as I know, this controlled experiment was never done. I am going to guess that the higher pitch prop will just bog the outboard down and you will actually get a lower peak speed.