under powered is miserable - 135 optipop was a V6- the 115 is a 4 cylinder- there is a lot more than 20hp difference in the functional power from these 2 engines. The used optis do sell cheap- wonder why? you know why. You can get can get a new 4 stroke 150 merc for a few bucks over 10k- with a simple plug and play adapter your wiring and control will fit-
I have a clean 135 Merc, 25 inch, 1994 model, ready to bolt on and go. You could be back on the water for 1500 bucks....plug and play
1978 Mako 19 with 90hp johnson 1996 Mako 22 1982 Mako 171 Angler 135 Black Max Mercury 1987 21b 225 Yamaha 1974 23 inboard Gusto gone. 1979m21 225johnson "blue dolphin" bought off this board and restored with everyone's help!!Gone but not Forgotten.... 1979 20 Mako 115 Suzuki gone 1977 19 Mako 115 Johnson gone 1976 23 Mako twin 140 Johnsons gone 1983 224 with closed transom and bracket And 160 SOB (some other boats) Venice Florida, Traverse city Mi.