Transom Replacement: Jon Boat Maintenance Guide

Jon boats are small boats that are typically made of aluminium. Over time, the wooden transom of a Jon boat will rot and need to be replaced. The process of replacing a transom involves removing the old rivets, fabricating a new transom, and installing it in the boat. This can be done using a variety of materials, such as plywood, epoxy resin, fiberglass, and marine sealant.

Removing the old rivets

Firstly, identify all the rivets that run through the transom. In most cases, there will be around 16 rivets, but this may vary depending on the boat. Once you have located them, use a Sharpie to mark each rivet head with a black dot. This ensures that you do not accidentally drill out a good rivet.

Next, you will need a drill and a spring-loaded punch. Use the punch to create a small divot on the rivet head; this will help guide your drill bit and prevent it from slipping. Drill each rivet head carefully, stopping as soon as you are about to drill through the head. You want to avoid making the hole in the hull any bigger than necessary. Repeat this process for all the marked rivets. Once you are done, the transom should be loose and ready to be removed.

It is important to note that drilling out the old rivets is a challenging task and requires precision and patience. Take your time and work carefully to avoid damaging the hull or creating unnecessary stress on the boat.

Additionally, consider wearing safety gear, such as eye protection and gloves, to protect yourself from any debris or sharp edges during the drilling process.

By following these steps, you will successfully remove the old rivets and be one step closer to installing a new transom on your Jon boat.

Choosing the right wood

When it comes to choosing the right wood for your Jon boat, there are several factors to consider, including the type of boat, your budget, the desired lifespan, and the intended look. Here are some of the best options for boat-building woods:

Plywood

Plywood is a good option for small DIY boats or temporary fixes. It is affordable and readily available. However, for bigger boats that require sturdiness, other types of wood are recommended.

Cedar

Cedar is a popular choice for boat building due to its unique features. It contains natural chemicals that prevent rot and repel insects, and it also has anti-weed properties. Cedar typically has a tight grain, which makes it easier to work with than other woods. There are different types of cedar, including Red, Yellow, and Lebanon cedar. Among these, Yellow Cedar is generally the sturdiest and most rot-resistant. However, cedar requires more maintenance and can be toxic and expensive.

Ash

Ashwood is another great option for boat building as it has good rot resistance and tends to bend and shape better than other woods. This allows for more creativity and rounded shapes in your boat design. Additionally, its strength-to-weight ratio makes it an attractive option. However, ashwood can quickly lose its colour to sunlight and cause fading.

Teak

Teak wood is widely regarded as one of the best boat-building materials due to its strength, density, and durability. It contains natural chemicals that prevent rotting, and it can be bent and played with, making it ideal for stress tests. Teak is more durable and water-resistant than similar woods like mahogany. However, it is quite expensive and challenging to find in large sizes. Teak also requires close attention and maintenance to maintain its integrity and appearance.

Mahogany

Mahogany is another popular choice for boat building. It is naturally dense, durable, and has a long lifespan. Mahogany is highly resistant to rot and decay, and it is easy to work with both by hand and machine. However, it is a heavier wood, and its colour can darken over time with continuous exposure to sunlight. Mahogany is also relatively expensive and requires consistent maintenance.

White Oak

White oak is commonly used for exterior marine surfaces such as decks, gunwales, and hardware mounts due to its density, hardness, and strength. It has excellent decay resistance and is highly resistant to swelling and shrinking when wet. White oak is also suitable for steam bending when green.

Marine Ply

Marine-grade plywood is specifically designed for use in marine applications and is often used for transom replacements in boats. It is made with durable face and core veneers and a waterproof adhesive, making it strong and resistant to moisture.

Fabricating the transom

Step 1: Remove the Old Transom

Before starting the fabrication, you need to remove the old transom from your jon boat. Identify all the rivets holding the transom in place and mark them with a Sharpie. Carefully drill out the rivets, being mindful not to make the holes in the hull any bigger than necessary. Once all the rivets are removed, the transom should be loose and ready for removal. Take this opportunity to inspect the hull for any additional work that may be required.

Step 2: Determine the Transom Thickness

It is important to determine the thickness of the original transom. In most cases, wooden transoms in smaller boats are made of plywood with a thickness of around 1". While you may be tempted to add extra thickness for future motor upgrades, it is advisable to stick to the original design to avoid alignment issues.

Step 3: Create a Template

Use the old transom as a template for creating the new one. Some parts may be missing due to rot, so do your best to estimate those areas when tracing the template. You will be using pressure-treated plywood for the new transom, so create the template accordingly.

Step 4: Cut and Glue the Plywood

Cut out two pieces of plywood using the template you created. These two pieces will be glued together to form the final transom. Clean the surfaces of any sawdust and loose wood, then apply a light mist of water to enhance the adhesion of the glue. Apply a generous amount of glue in a checkerboard pattern on one of the pieces and firmly press the two pieces together. Use clamps or weights to hold them in place and let the glue cure for at least 48 hours.

Step 5: Sanding and Fiberglass Resin Application

Once the glue has cured, it's time to sand the transom. Use a palm sander to level the edges and remove any excess glue. Clean the wood to remove any dust, then apply a copious amount of fiberglass resin to both sides of the transom. Let the resin cure overnight, then flip it over and repeat the process for the other side. Lightly sand the transom again if needed.

Step 6: Reinstall the Transom

Drill holes through the transom at the marked locations for the rivets. Apply a marine sealant, such as 3M 5200, to the holes and insert stainless steel carriage bolts with washers and lock washers. Tighten the bolts securely and allow the sealant to cure for 48-72 hours.

Step 7: Finish with a Transom Cap

If the original aluminum cap along the top edge of the transom cannot be salvaged, you can replace it with extruded aluminum "L" pieces. This will give the transom a nice finished look. And that's it! You're now ready to bolt on your motor and get your jon boat back in the water.

Applying fiberglass resin

When applying fibreglass resin to a jon boat, there are several steps to follow. Firstly, you need to prepare the boat. Remove any items from the bottom of the boat that you don't want to be covered in fibreglass, such as the keel, lift stakes or rails. Then, repair any holes with an appropriate filler. Next, clean the hull of the boat, ensuring it is free of debris, barnacles, dust, dirt and mould. It is important to then sand the boat, creating a rough surface for the resin to adhere to.

Now, you can begin the process of applying fibreglass. Mix your resin and hardener according to the package instructions and pour the solution into a paint tray. Using a foam roller, apply the first coat, also known as the seal coat, with firm pressure and directional strokes. Once this coat is no longer tacky, prepare and install the fibreglass cloth by cutting it to shape and attaching it to the hull with tape, tacks or staples.

Apply the second coat of resin, known as the bond coat, over the fibreglass cloth. Ensure you remove the tape, tacks or staples before this coat sets. You can then apply a third coat, the fill coat, and finally, a fourth and final coat, the finish coat. This final coat should be thick enough to allow for even sanding without damaging the cloth.

Once the final coat is dry, preferably left overnight, you can begin to sand the hull, starting with lower grit paper and finishing with a higher grit paper. Finally, apply a protective agent, such as paint or another boat hull finish, according to the package instructions.

Replacing rivets with bolts

When replacing the transom of a Jon boat, it is important to consider the type of wood and sealant to be used. While some recommend exterior-rated plywood like BCX, others suggest using marine-grade plywood and treating it with penetrating epoxy to make it waterproof.

Now, if you are replacing rivets with bolts, here are some detailed steps to follow:

Step 1: Measure the Rivet Diameter

Use calipers or a tape measure to determine the diameter of the rivet. Calipers will provide a more accurate measurement, especially for smaller rivets.

Step 2: Select the Correct Drill Bit

Choose a drill bit that matches the size of the rivet. Ensure that the drill bit is secure in the drill motor. Avoid using a bit larger than the rivet to prevent enlarging the hole, as this may weaken the holding capacity of the replacement bolt.

Step 3: Drill Out the Rivet

Place the tip of the drill bit into the center hole of the rivet and drill it out. A properly sized bit will leave only the top "ring" of the rivet around the drill bit. Remove any debris from the hole.

Step 4: Remove the Rivet Ring

Use pliers to twist and remove the metal ring that is left around the drill bit. Twist it in a counterclockwise direction.

Step 5: Insert the Bolt

Place the bolt into the drilled-out hole. If you are using a machine bolt with a nut fastener, hold the nut in place with pliers while tightening the bolt with a screwdriver. Ensure the bolt fits snugly in the hole.

Step 6: Repeat for Additional Rivets

Work on one rivet hole at a time to avoid removing too many rivets at once, as this could weaken and misalign the metal structure. Repeat the process for each rivet that needs to be replaced.

By following these steps, you can effectively replace rivets with bolts when working on your Jon boat transom or other similar projects.

Frequently asked questions