I bought my motor from Denver Boat Shop - Boat Repairs and Tohatsu Parts and Accessorries
and they sold me a flatter prop at the same time. I think 9 deg stock changed down to 8, still 3 blade. Not sure if a 4 blade would work even better or not. They might be able to help order exactly what you need. It's a wooden front door with repairs in the outbuilding kind of place, but they seem to know their stuff. I know how to pull the starter cord, but not all that much more beyond what I can Google.
My set-up pushed my cataraft plus a 3 wide barge across the front without much difficulty.