Boat seats mount to the sole or floor, of a boat, and the method of attachment depends on the type of seat. Bench seats and lounge sleeper seats are supported by a console base. Single seats and swivel chairs are supported by a pedestal and base plate. Attaching a console to the deck is relatively easy for the average DIY person. Attaching a pedestal to the deck requires a few more steps to ensure that the elevated seat remains secure in all conditions. Attach boat seats using marine hardware and basic carpentry tools.
Lift the bench seat or lounge sleeper off the console. Position the console on the sole of the boat at the desired location. Reach down through the open top of the console and mark the floor along the inside edges of the console to make a reference for the attachment.
Cut two pieces of 1-inch-by-3-inch mahogany to fit against the longest inside edges of the console from corner to corner. Cut two additional pieces that fit between these pieces at the short sides of the console. Drill 1/16-inch pilot holes for screws at 4-inch intervals in the 3-inch wide face of each piece. Refer to your reference marks to make sure the console is in the precise location as marked.
Apply silicone adhesive to the 3-inch wide face of each mahogany piece and set the pieces in place against the inside edges off the console. Make sure the adhesive is on the underside of the pieces and contacts the sole of the boat. Drive 1 1/4-inch wood screws into each pilot hole in the faces of the mahogany and into the sole or floor of the boat using a cordless drill with a screw tip.
Position 2-inch-by-2-inch predrilled stainless steel corner brackets on the mahogany strips and against the sides of the console.
Drill 1/16-inch pilot holes for screws that attach the base of each bracket to the mahogany. It is not necessary to drill pilot holes for the brackets on the inside face of the console. Typical seat consoles are made with laminated plywood that receives wood screws easily. Install 3/4-inch wood screws into the upper section of each bracket in the pre-drilled holes and into the sides of the console. Replace the bench seat or lounge sleeper onto the console.
Turn the single seat or swivel chair over on a piece of carpet or heavy cloth to protect the finish. Refer to the seat installation instructions and determine whether the plywood seat bottom can be removed from the seat. If it can be removed, bolts with nuts will be used to attach the upper pedestal plate to the seat bottom. If the seat bottom cannot be removed, wood screws will be used to attach the plate.
Lift the upper swivel plate off the top of the pedestal and position it in the centre of the plywood seat bottom. Mark an outline of the upper plate for reference.
Apply silicone adhesive to the underside of the upper plate. Position the plate on the centre of the seat bottom. For bolts, use the pre-drilled holes in the swivel plate as a guide and drill 1/8-inch pilot holes in the seat bottom at each pre-drilled hole. Attach the swivel plate using 1-inch bolts with nuts. Replace the bottom onto the seat using the removal procedure in reverse. Proceed to the next step if the seat bottom does not remove from the seat.
Apply silicone adhesive to the underside of the upper plate. Position the plate on the seat bottom and attach it using a 1-inch wood screws into the predrilled holes on the plate. Install the screws with a cordless drill and screw tip attachment.
Position the base plate and pedestal on the sole or floor of the boat at the desired location. Use the predrilled holes in the base plate as a guide and drill 3/16-inch pilot holes through the sole or floor for stainless steel screws at each hole. Remove a nearby hatch cover to access the underside of the sole or floor at the location of the pedestal.
Apply silicone adhesive to the underside of the base plate. Align the pre-dilled holes in the plate with the pilot holes on the deck. Insert 3/16-inch stainless steel bolts in each hole. Put flat washers on the threaded end of each bolt below the sole or floor of the boat. Secure the base plate attachment with nylon locknuts and a socket and ratchet.
Replace the hatch cover on the sole or floor of the boat. Sleeve the upper plate on the seat bottom onto the top of the pedestal. Repeat this procedure to attach additional pedestal seats on the boat.
Consult a shipwright or boat shop for methods to attach corner brackets to certain materials used to make seat consoles. Bolt sizes for pedestal attachments vary. Refer to the installation instructions and drill the appropriate size pilot holes for the recommended bolts.
Do not drill into the hull of the boat to attach seats. Consult a shipwright or boat shop for attachment methods.