need to replaced floor......help

My floor is VERY soft around the drivers seat and pylon but very sturdy along sides. How would I go about fixing that. I pulled some of the carpet up i thought it was just a piece of wood like in the back but it looks like fiberglass maybe with wood on the inside. does that sound right. what would be the corect way to fix this.

the stringer system in your boat had a double thick piece of plywood from just in front of the ski pole to just in front of the battery box. in order to repair you pull carpet back to motor ,take out seats,battery. use circular saw and set depth to 1/2in. cut out from ski pole to side of hull on both sides then cut along the edge to front where the floor stops at the hump,then cut across by battery box. remove board and inspect stringers,if rot is found you need to dig out bad wood. then use a product called git-rot. follow instructions on its use. use old board for pattern and cut and fit new into boat. before u fiberglass board in resin coat underside of board. hope this helps.

The rot doctor's stuff is great cost a little more but works, git-rot is a waste of money. I used the rot doc CPES and a badly rotted section of wood under the rear seat with half of the wood gone. applied the CPES now its hard as a rock.