I am getting similar speeds with a 25 hp Yamaha 4 stroke in my 14 foot Crestliner which is lighter than your boat. Regarding props Yamaha stamps the diameter of the prop on the side of the hub but you have to remove the prop to find the pitch. My prop is 9 7/8" diameter but I will let you know what the pitch is when I pull it off.
Optimizing a propeller is hard to do if you do not have a tachometer to see full throttle throttle RPM . If it is below the recommended operating range you need less pitch. If it is above recommended you need greater pitch. Evinrude motors have a chip hat can be read by dealers that shows max rpm but I do not know if Yamaha has the same feature.
The most common cause of water pump failure is running the motor with no cooling water which lubricates the vanes of the displacement pump. Even a quick bump of the starter to check the battery connection will wipe material off the vanes and affect pump efficiency.
