http://yamahaoutboards.com/propeller...ng-a-propeller
Hope the above link helps you w/prop choice...when i went to a 150 Honda back in '04, I had help from a Honda Factory Tech...wound up w/a 15 1/4D X 17P 3 Blade made for Honda by Power Tech Props...and I believe you should be looking in that spec range on yours...
ONE THING yer gonna notice about this re-power is vibration...as in the LACK OF IT...ya don't really notice it til it's gone...will never forget it...felt like I had stepped into a NEW BOAT...
Take the camera w/you when you splash the new power cuz we wanna see...we wanna see!!...