hi john

the exhaust pipes are pretty bullet-proof. i doubt there's a hole. you'd get alot of hot water coming in the boat if that were the case. if you wanted, you could remove the exhaust hoses and pour a gallon down each pipe, see if a gallon comes out the other end. this is what you're dealing with, w/o the deck and foam (your stringers or engine area might be slightly different):



if you can zoom in where the exhaust exits the transom at the top of the pic, you'll see that there's not much to it. 6 or 8 screws thru the fiberglass.

you can also get a look at the inside of the bracket bolts in that pic. good chances your hardware is crusty behind the transom.

you could get away with just opening up the floor in the three areas where your platform brackets are. just big enough to get a wrench on the nuts. i think sealing the exhaust pipes is probably enough. however, most likely, you've got soaked foam. the stringer areas where the motor mounts attach to don't do well with standing water. if you open the floor, dig down to the hull and see if the foam squishes water out. good luck