[willy]

I would spend some serious time thinking about that one, if you do it closing the hole up the right way and adding a good quality flotation type bracket is the only way to do it right. As Skools said creating a notch is not an option.
On the other hand you have a working system, You can buy a brand new motor and rebuild the outdrive for a lot less than the cost of an outboard alone.
I have fished many times on friends I/O's and love em. They can be worked on in most cases just like we used to work on car engines and if I owned one I would spend some time with a guy like Ferm or Skools and learn how to maintain and work on the outdrive myself and you will have a fuel efficient and fast reliable set up.
Yea I would re-think that one
Also I have a fellow in my marina that has an older 28 foot cabin cruiser type boat, he stays on it weekends and fishes all the time with it. Single I/O, I believe a Chrysler he said. Has done routine maintanence on her since new and has thousands of hours on her. He said he had paid a mechanic friend for his time twenty years ago to teach him how to take down and redo his outdrive years ago and he does his own every winter when she is on the hard. Uses very little fuel and pushes the boat to a nice cruise speed with a ton of room. If you can do regular maintainence on them they are reliable and strong and efficient.