I need to replace my old 75 merc 115hp that I have on a 1968 aluminum 17' Crestliner. I have been looking at two different motors that seem to be in decent shape. One is a 1981 115 Johnson and the other a 1989 Mariner. If everything is equal what would be your choice? Also as a side note, are the Mariners and Mercury's the same motor? Thanks for the input, I am really a novice at this boating thing.