Prop for Seafari 115 Merc I-6

[McGillicuddy]

Thanks guys.
In my shake down cruises with a light load I've determined that I am topping out @ 4400 rpm making 33mph by gps.
I seem to be getting on plane at about 12-13mph @ about 2500 rpms (not certain of this but close) but have not timed the rise from a dead stop to WOT. I also have a Stingray hydrofoil on it which I think is very helpful, although I have not tested it w/o. I got about 2.5mpg off a 6 gal test tank.

I finally determined the Al prop to be 12-3/4 x 21 R MWC. I have not removed it so I'm not sure if it has a model number on the inside.

The motor is an '83 Merc 115 I-6 with a 20" shaft that appears to be original. The gear ratio should be 2:1.
The motor is in very good condition with slight damage (not sure of the term) to the edge of the top piston. I believe the timing has been retarded to 21deg and the jets have been changed to better serve the upper cylinders with modern gas. For now I'm running 50:1 QS premium plus

The motor certainly pushes the load effortlessly with 2 guys 30gals and no gear or bait tank(I'm hesitant to fill the bait tank until I redo the scupper with new tubes and vortex).

I was thinking I might pay $70 or so for that Yamaha prop. What does it cost to change a hub if necessary? And How inexpensively might I find a more fitting used prop? Here some pics of the current situation. Thanks again for the expertise, guys.