1991 50hp Prop Size???

[nam6869usmc]

I bought a used 14ft Fisher with a rebuilt 1991 50hp that runs like top, and it has a 4 blade 10.8" 12P Solas on it. I've ran the boat about three times hard and it runs about 33mph using GPS (no tach), but without the Lenco TrimTabs adjusted Bow Down quite a bit it's porpoising extremely bad. I think I'm going back to a 3 Blade but in SS, but what I've read on here, it's hit or miss & thats $$$. I have the Stock Prop that came off the motor, but I don't know what size it is, it's stamped (48.38086 15 H E4453).
If I get a SS 3 Blade I would like to get close to stock but a little more speed > less pitch,,,,any help and or advice would be much appreciated..
P.S I checked Yamaha for that motor and they list a bunch of different sizes/

[99yam40]

see if this site will help

Performance Bulletin Home

[nam6869usmc]

see if this site will help

Performance Bulletin Home

Thx, learned a lot on that site, seems like a 10 5/8 x 12 is standard size, but the 13 5/8 x 13 had the highest speed/performance at 34.9mph. Now to find a SS with this size
Just went out & measured the clearance, 13 5/8 is to big, only a 11 5/8 will fit,,

[99yam40]

If you are happy with the performance of the prop you have,maybe you need to think about a tail or hydrofoil to help with the porpoising or readjust the load in you boat?

There are forums on propping boats that you may want to find and post questions that may give you more info.

Here is something on props I though was interesting.

Prop Slip Calculator