Re: 115 hp
There are different sources for different price ranges. A boat dealer will usually have some motors for sale. Normally they are not too old and several thousand dollars. A OB repair shop may have some older cheaper motors for sale.
I was lucky enough to have a boat junkyard (actiually two) near me. One of them had stuff from the '50s to the '70s, the other more current stuff. Unfortunately, the guy with the newer stuff had to go to jail for not paying the state it's sales tax, and his successor went to jail for a short time for stealing and then got foreclosed and the place was cleaned out.
So you are likely done to those two places and Craigs list and e-BAY
The place with all the old stuff is in business, but likely not applicable for you.