"Paul, anytime you alter the t
"Paul, anytime you alter the transom of a boat it affects the max capacity, the max horsepower rating and could cause safety issues since the boat was designed to have a 20" transom.
So you don't just want to get out there with a saw and start cutting away.
In a case such as yours I would only go with one of two options - convert your motor to a long shaft with a kit if available or used parts if you can find them. Either way it could be expensive (an aftermarket extension kit can run from about 700-1000 bucks).
Alternately, you can go with a mount or jackplate and just mount the motor a little further back and a little lower than the transom would normally allow.
That may look a little odd, require some creative rigging and you do run the chance of drowning the motor if you get hit from the back by a wave, but many commercial builders have gone to mounting the motor on a platform out back (looks like they are mounted on the end of a swim platform) and it appears to be working half decently for them.
But in any event, I really wouldn't look at cutting the transom unless you are prepared first do some research on the effect it will have and then possibly have to do alot of work (depending on the construction material of the boat) and then having to have the coast guard recalculate the capacity/max horsepower of your rig to ensure it's safe and can be insured."
