I recently bought a 1990 Wellcraft Eclipse 186 w/ a 4.3L, 2bl mercarburetor, Alpha One stern drive, Quicksilver 48 16316 A5 19P prop. (solid, well-kept, love at first sight-I think my wife is jealous). Its new elevation range will be 5000-7000 ft. (originally <1000ft). I know there will be a 15%...