Taking the Transom out

The interior of my 1978 Cutty Cabin is almost total mush. Tried to dig out the old wood with an electric chain saw. The chain saw worked great as far as it would reach 16". need a lot longer blade. Don't see a way to get to the remaining wet rot from inside the boat without removing the top deck, part of the interior flooring and motor well. To much to take apart and put back. Believe the best repair method is from the outside to come in about 2 inches from the sides and bottrom. Using a side grinder bevel both sides of the 2 inch line until I grind through to the rot. Dig out the rot. Insert epoxy coated plywood. Pour an epoxy filler in the 2 inch area at the bottom. Bolt on the portion which was cut out and start filling the voids with an epoxy filler. Once the transom is filled refiberglass the transom and paint. The entire boat needs painting.

If there is a better and/or simpler way please let me know.

Would not be surprised to read GET ANOTHER BOAT. Bought the boat with a 2001 Yamaha V150 with only 51 hours on the motor, it also has a 2001 SeaStar 1.7 front-mount hydraulic steering system.