Help with Prop.

I have a 18ft Bayliner Bass Boat With a 150 Pro v Yamaha and the other day my pro came off in the lake so i need to get one but dont know what pitch it was What do you guy recomend i get everyone teels me i should be about 60mph but was only getting 50 out of the other one.

[boats.net]

Maybe start with a 23 pitch and work up or down from there.