Old Houseboater is right on - Pressure treated is real iffy to glass to. regular exterior is fine to use. I would suggest that you prep it first by sealing it with a penetrating epoxy sealer - a quart should do- about $50.00 and well worth it. The glass will bond much better and make the ply very water resistant.

Almost all outdrive Nautalines have a transom rot problem, this may be as Joe says partially from neglect. Usually the stringers are from water sitting in the boat (Neglect). There was some defect in the outdrive gimblehousing somewhere as the water would get in and rot the wood. This is common on many boats. The Burnscraft was the least prone too this for some reason. Could be because they were hand laid and Chopper guns were used on Nautalines. Had a Seagoing that the whole stem broke on. Sat with water in it for a couple of years

The problem with Nautalines and transom rot I feel is due to the outdrive used (mostly Volvo 270 or 280) The way the bolts go through the transom outside of the rubber sealing ring invites water seepage into the transom where it wicks into the plywood endgrain. It won't leak into the interior because most installers really glop on the silicone on the under side of the washers on the interior of transom and then crank down the nuts holding on the outdrive. These bolts/holes need to sealed at installation on the underside of the mounting ring and then the bolt holes FILLED with sealant and then push the bolts through. This will keep the water off the endgrain inside of the bolt holes. Personally when I get ready to mount one I drill the holes then epoxy saturate the bolt holes first and let it cure then I use urethane sealant - not silicone- on the under side of the mounting ring and the bolt holes and washer undersides and coat the shank of the bolt when I insert it.

Joe just gave some very good advice, I use Boatlife polisulfide sealent for under or above the waterline. I use it above as well as below on everything, it works very well.