I am new here so take my recommendations with a grain of salt. I have a aluminum 17ft tracker. I had the 40hp merc to start, with a 10.5x13 aluminum prop. I tried a 11x13 ss prop and felt that was a almost perfect setup. I went to a 60hpmerc with the same 11x13ss prop and feel I am now under propped. With a 50hp I know a friend that is running a 11x14 on his merc. 50hp. I think one of the three props I mentioned would be good starting points for your boat and I would probably start with the 11x14 aluminum with your light boat, but the 10.5x13 might be a bit easier to find in a used prop.
