Old 50’s mercury outboard value?

[lehman live edge slab]

I have a good friend cleaning out his basement and he wanted to try and gauge the value of his old mercury 7.5 hp outboard with the original stand and owners manual. His grandfather bought it new and I bet it hasn’t burned 2-3 gallons of gas since new. He used it 1 or 2 times and it’s been stored inside since. He wants to clean the basement up so it’s going and maybe even to me but I want to be fair about it.

 

[Johnmn]

@Stevetheboatguy