Merc 500 Thunderbolt on a 15 foot Mirrocraft. What pitch prop?

[Roadblock]

I have a 1970's Mirrocraft Titan 15. You can see the boat specs on the attached photo. Weight, length etc.

Boat has a 1970 Merc 500 Thunderbolt 50HP. How would I go about selecting the pitch that would be best suited for this boat?

When I bought the boat it has a Michigan Wheel 10 1/4 x 13 prop on it. Obviously this was not the prop that came from the factory. Runs good, no complaints. Does about 25~30 mph. Unfortunately I broke my prop. I need to get another prop and all I can find that is a directly replacement locally is a 10 1/4 x 11 and a 10 1/4 x 12 pitch.

Hell I don't even know if the 13 pitch was right for this boat to begin with. Unfortunately I have no RPM gauge so I don't really now what it ever ran at.

I'm curious to hear what some of you guys who understand this stuff think the pitch SHOULD have been for this setup based on the weight and length etc.

Thanks!

 

[bgc]

http://www.propcopropellers.com/mercury_Outboard_Propellers.htm

Im running a 12 for just running on the water with minimum weight and a 10 for water skiing. 15' Starcraft JetStar(aluminum), 1100# loaded.

 

[Roadblock]

I know this post is OLD but I had the boat stored for a few months.

So you go lower pitch when your pulling? I have a 12 and 13. I normally have the 13 on there, wonder if trying the 12 pitch would be worth-while. Not much of a different but who knows.