" The Michigan prop you have i
" The Michigan prop you have is about 15x17RH (Volvo #814616). This is about the right size for you boat. Since you dident state your full throttle RPM I cant give you a rec. on how to tune it. How ever if your RPM is in the correct range with this prop, and you want a little more top speed you can switch to a 14x19 and not affect the RPM. The boat will be a little slower to get out of the water, could affect your skiing.
A word of Caution, Do not over rev your 125, it will toss a rod. I've seen it many times! I have a 14x19 in stock (Volvo part# 814633) I can sell you for $130 NEW. ( List is $182.65) "