When the O'DAY 23-2 was built (1977-85 model years) the average weight of a 2-stroke 9.9 would have been around 75#. As to which side to mount outboard on, One factor is transom re-enforcement, If original was on Starboard side, plywood backing might be molded in there, or maybe backing was added on port if that was aftermarket. I have always had my outboards mounted offset to port, and that worked well for me. However, one thought is that an off-set outboard affects turning, so if it is advantageous to be better at turning to port, mount outboard to Starboard. If you more often need to turn sharply to starboard, mount motor to port. With my outboard mounted to port, the boat will turn better to starboard under forward power, and if backing, turn better to port (that is In reverse, the bow moves to port, helpful as I back away from my mooring line located off the starboard bow.) With most motors, the tiller is offset to portside of engine, shift lever either on front of motor of on starboard side. So, with outboard mounted to port the OB tiller is farther from boat's tiller and shift is between OB and rudder. Mount Outboard to starboard and tiller is closer to the rudder/tiller of the boat and shift is away from tiller (unless on front of motor as some newer ones are). I like Outboard on one side of boat, battery offset to other side for balance, but if you have electric-start and/or a battery charging coil, how long are the cables? Will they reach from outboard to battery, or will you need to extend them? I like the idea of locating the battery amidships under the companionway, but that may be a long run for the cables, plus the O'DAY 23 has a built-in ice-box there (does anyone actually use it as such?). I think originally, O'DAY located the battery box in the cockpit sail locker.
