Prop exchange options?

[eavega]

So, I have my 1972 50 HP Evinrude running as it is supposed to (Max 6000 RPM, WOT 5500-6000 RPM) with a 13p prop. Whatever previous application the motor had, it was running a 17p prop (which I believe was the standard prop for this motor when new). I really wanted to have a spare prop 'just in case' and was thinking of either getting another 13p or possibly a 15p to see if I could get a little better speed (The 17p would spin at 4500 RPM or so, so I guess the boat was too heavy to be pushed by the higher pitch prop). I was wondering if anyone knew of a shop that might allow me to "trade in" the 17p prop for some kind of credit towards another prop, either new or used. I'd rather trade it than have to go through the route of selling the 17p first.

-E