Hate to keep dragging up an old thread, but that first picture was so crappy, I wanted to show what really went into building the motor mount...
The back of the dinghy had "lugs" that were designed for an optional electric motor sold by West Marine..
I wanted to incorporate them into the design so I built a transom out of marine ply and added "hooks" that clip into the lugs in back
Needed some side to side stability as well as transfering torque to a greater portion of the dinghy so I fabricated longitudinal stabilizers (braces) out of copper pipe from transom to oar locks...
These in turn are secured to the oar locks with clips
And to the transom with "J" hooks tightened from the back...
The mount seems to support the 3 hp 2 cycle (24#) motor rather securely...
And folds into a compact package for storage...
