I am known for not being popular on here with my opinion, so I wil stay true to form and suggest buying something a little newer. A new Yamaha 50-70 should cost about 5k with controls and wiring. Check it out really good if you buy it. A fifteen year old outboard can be a big problem if it was not well taken care of. The boat can handle a big motor if you build it rightOK, so I'm going to check out this 1995 model 85 HP yamaha on Friday. The deal is $1100 for the complete motor, wires, controls, & gauges.
It might work with your prospective motor if it is a three blade, and it would probably be way too much if it is a four blade. I am not a prop guru but I am using a 13 pitch four blade prop on my boat. It has a little too much bite though I have ground it twice to relieve some of the cup.For an extra $100, I can get the 19 pitch SST prop. But I'm thinking that this pitch is no good for the XF20.
Shot of the barge....
Richard