RC, or remote control boats, run in the water just like their larger counterparts. Only they have electrically operated servos, controlled by electrical inputs, that allow them to manoeuvre, pick up speed and stop. Contrary to their miniature size, remote control boats take on water just like full-sized boats, and one of those areas involves the boat driveshaft. The typical RC driveshaft uses a universal joint driven off the engine to propel a shaft through a stuffing box. The shaft exits the hull and connects to a propeller. Sealing the driveshaft against leaks requires a few steps, tools and products to perform the procedure correctly.
Set the RC boat on a workbench, cushioned underneath by some foam or rags. Examine the location of the driveshaft where it exits the bottom of the boat. Look for cracks in the wood or fibreglass, depending upon the construction type. Use a screwdriver to loosen and remove the front driveshaft universal joint set screw. Use the screwdriver to remove the rear universal joint set screw in front of the strut location. Refer to their location in your owner's manual.
Use a screwdriver to remove both front and rear coupler set screws on the driveshaft. Pull the driveshaft out of the stuffing box. Clean the driveshaft with steel wool and carburettor cleaner. Wipe it dry with a rag. If the stuffing box tube appears loose in the hull, use pliers to twist it from side to side and pull it out, but remember its depth position in the hull.
Clean the inside of the stuffing box with carburettor solvent and a pipe cleaner. Wipe the outside of the stuffing box tube with acetone and dry buff with a rag.
Clean the inside of the stuffing box tube guide hole that goes through the hull, with acetone and a pipe cleaner. Use a pipe cleaner to coat the inside of the guide hole with marine epoxy adhesive. Apply epoxy adhesive on the stuffing box tube and reinsert back into the hull hole, in the exact position it came out.
Wait for the adhesive to dry. Insert marine stuffing box grease into both ends of the stuffing box, pushing it into the tube ends with a pipe cleaner. Apply stuffing box grease on the driveshaft and insert it back into the stuffing box tube.
Connect the front driveshaft coupler set screw with a screwdriver. Connect the front universal joint to the front coupler and tighten the set screw.
Connect the rear coupler to the driveshaft and tighten the set screw with a screwdriver. Connect the rear universal joint to the rear coupler and tighten the set screw. Use some 400-grit sandpaper to sand the area around the stuffing box tube on the inside of the boat and the outside. Wipe clean with a rag.
Apply a bead of waterproof silicone around the stuffing box joints on the inside and outside of the hull. Wait for it to dry at least 24 hours and test the boat in the water.
If you are running nitro fuel in your RC boat, it is a good idea to remove the engine and servos and repaint the inside of the boat with a good quality gel coat marine epoxy. Nitro fuel will eat away at the finish, disturbing the seams and seals, as well as the protective hull finish.