I installed a Yanmar 2GM20F into my 1977 B240-TM.
It is coupled to a Yanmar Saildrive SD-20
Outboards hung on the transom is a poor idea at best, It upsets the righting moment, Center of gravity and center of buoyancy.
This cannot be designed for as not all outboards are created equally.
By putting the weight as low as possible and inline with the keel you can add stability and eliminate the lever action on the transom.
She is currently for sale if anyone is interested, Located in northeast Ohio 44004.