Unfortunately the use of wood products (Plywood) has proven over the years to be compromised from the elements. The use of plywood in ,stringers, floors, exterior supporting bulkheads, cleat butt blocks, anchoring points, engine beds, swim platforms, and seats has slowly become obsolete. In the 90's the big selling point of many major boat manufactures " we use no wood below the water line, stainless steel or aluminum used for all backing plates, roto cast or starboard used in all seat bases". After the 90's and into the 2000's that selling point went away because most manufactures caught on to this new way of building boats. Better polymer products were introduced into the market and better building techniques. The use of wood products for structural or exterior components is used in a minimal capacity and when it is used it is normally sealed and encapsulated in resin, all four sides to eliminate or greatly reduce the chances of water absorption.
Unfortunately Fluid motion uses wood products in structural components and also decks, seats and backing plates relying on thin Stainless steel fender washers for added backing. The wood is finished with gel coat on one side, raw open wood on the other side in many places. This build is structurally very sound but if it gets wet or sits in a wet environment can be compromised. It is unfortunate that your seat bases are rotted. I would recommend using starboard to replace the wood. It will never rot. I would also recommend as part of preventive maintenance to make sure compartments are dry and any open holes in wood components are sealed. Add some ventilation to storage compartments for air circulation to reduce moisture and mold. Keep all your limbor holes cleared so that water doesn't sit under the floors and the water makes its way to the bilge. Inspect your swim platform, deck fittings and fasteners. I have water dripping at every swim platform mounting surface area and have noticed loose screws. If I tighten them the thin fender washers start to mushroom the wood has no backing because it is soft. I have found 2 engine mount lags loose( I was surprised to see wood still used in the engine bed, I haven't seen that since the 90's. I have a 2016 Cutwater stored 6 months a year in heated storage, I maintain my boat and know every inch of it. I keep finding issues. There are many places that I am impressed by the innovation and ideas put into the build. Unfortunately there are many places that short cuts and quality control issues keep popping up. If I didn't like the boat I would sell it and move on to something else. I'll keep complaining, fixing, repairing, Commiserating with other owners, and enjoy my boat. Good luck in the repair of your seats.
