Building a homemade pontoon boat can be easy if you are relatively comfortable with do-it-yourself building projects. You will need some basic construction materials--most of which can be found at home-improvement stores.
Building a pontoon boat yourself can be more affordable than buying a pontoon boat, as long as you follow the proper steps to construct the boat safely and durably. Before you get started, read about fluid dynamics and buoyancy so that you can build a boat light enough to float on the pontoons you select.
Develop your boatbuilding plan with the help of a contractor who understands weight and buoyancy or find a plan or boatbuilding kit. Redesign, tweak, and expand the plan as necessary to suit your needs. Specific measurements for your pontoon boat will depend on the plan you choose or develop.
Select your build site. Construct your pontoon boat either close to water or be prepared to use a trailer to transport the finished boat to water.
Obtain two or three pontoons. Pontoons are the only part of the boat that touches water. They are hollow, cylindrical objects that keep the boat afloat by displacing water and balancing the boat. To find the right pontoons for your building plan, scour scrapyards to find large PVC water pipes, plastic drums, or surplus military drop tanks. Look for objects that are aerodynamic, as they will also be hydrodynamic.
Purchase or select your boat-framing and construction materials. Look for marine-grade plywood or another kind of water-suitable lumber.
Waterproof your pontoons and place them parallel to each other on flat ground. If you are using PVC pipes, waterproof them with a glued slip cap, hub-and-band system, or a wooden plug held in place with epoxy and screws.
Construct the body of the boat according to your boatbuilding plan. Install cross beams to support the deck and hold the pontoons together. For extra bracing, use galvanised straps, wrapped corner to corner across the beams. Add edging or rails for safety. Consider adding a bench or canopy.
Build a strong motor mount to hold the motor in place at the centre stern of the boat, if adding a motor. The motor mount should be installed low enough on the boat so the motor can be submerged in water. You should also be able to tilt the motor to control the direction of the boat.
Seal the boat with resin for extra waterproofing. Use waterproof silicone to seal any edges, holes, seams or other areas where water could potentially leak into the pontoons or boat body.
Test the boat for durability and buoyancy to ensure safety before taking it out on a body of water.
When using your pontoon boat, be sure to have a personal flotation device readily accessible for everyone on your boat; it is not only safe in the event of an accident, but it may also be a law in your state. You may want to have a contractor inspect your boat before taking it out on the water to be sure it is durable and safe for use.