Construction of a Pontoon Boat

by Dave on January 9, 2010

In the modern age, almost every pontoon boat that is constructed is made from aluminum. The reason that companies and boat manufacturers use aluminum is that it is a very light metal, and it does not rust at all. To make the log shaped pontoons, sheets of aluminum are rolled and then welded into cylinders. The cylinders do not cover the boat from aft to stern, they slant upwards as they get to the stern of the boat, this is necessary so the boat will be able to move forward with a very small amount of resistance.

If they were just flat you would need a lot more power to move the boat, and that would be poor design as you would be wasting money on fuel. There are anywhere from 2-3 cylinders, but actually there are a lot more than that. Just to make up one, several cylinders are welded together with each having its own water tight compartment, so if a hole gets punctured in one of the cylinders then there are many more water tight compartments to keep the boat afloat.

Boat builders can choose from different kinds of aluminum, it will all depend on what size boat that they will be building. It isn’t extremely important on what grade aluminum is used if you plan on using the pontoon boat in freshwater. But if you plan on using the pontoon boat for saltwater you will want the highest quality that you can get, as saltwater has the tendency to corrode metal.

There are three main types of logs that are used on pontoon boats, these are the traditional round logs, U-shaped logs, and boat shaped bottom logs. The boat shaped bottom logs, or pontoons, are made for speed, so if you want a boat that travels fast you may want to look into a boat that has these. The traditional rounded logs are rarely used these days in pontoon construction as there are many other factors that can be easily upgraded to contribute to better speed, and better deck attachment. U-shaped logs are probably the most popular logs that are used in pontoon construction, as they provide great buoyancy and are easier to assemble to the beams that connect the 2 or 3 pontoon logs.

The 2 or three pontoon logs are attached together by aluminum bridge beams, and they are generally 16 inches apart. The beams are either connected to the pontoon logs by means of welding, or by nuts and bolts. If the boat is using nuts and bolts then they will have to be inspected annually to make sure that they are still tight, while if the cross beams are welded onto the pontoon logs there would be no need to check up on the tightness.

Once the beams are intact then a boat builder will start adding the deck, which is almost always made of plywood that has been pressure treated so the wood will not rot. A few reasons why boat builders use plywood as a deck over metal are metal decks get hot easier, this would be bad on a hot sunny day. Another reason is that would absorb vibrations and sound a whole lot better than metal does.

Once the deck is mounted onto the cross beams it is usually outline in a finished aluminum for looks and support, and they marine carpet is added on top of the deck also in most cases. From there the boat builder could install railing and furniture on the boat which is mounted to the deck, now for the main design all that is left to do is install the motor.

Pontoon boats almost always use outboard motors, and the mounting of the motor is easily done by use of a motor mount that is installed between the pontoon logs.  I have not seen many pontoon boats that have more than one outboard motor installed on them but I am sure that it possible and there are some out there with dual motors.

Now that the main design is done there are many other things that could be added to the pontoon boat. For instance Crest along with other pontoon boat manufacturer’s have models where an aluminum sundeck is mounted to the frame, giving the pontoon boat another floor. Ladders are often installed on new pontoon boats, and can easily be installed if you have a boat without one.

{ 11 comments… read them below or add one }

piator January 13, 2010 at 6:46 am

I am interest with pontoon boat and want to know construction

Larry Sozak February 10, 2010 at 4:55 am

I’ve been looking into getting a pontoon boat myself, and I found it interesting that the type of aluminum is a major consideration in salt water. That’s something I wouldn’t have considered, but certainly will ask about moving forward.

jim gardas March 7, 2010 at 4:02 pm

good info. What exact grade of aluminum is used. I looking to do some TIG weld repair.

TOOTIE March 14, 2010 at 4:56 am


Jim Abraham May 10, 2010 at 7:12 pm

I have a 26′ pontoon boat with 3 logs. Right above my middle log I have a 12″ X 12″ soft spot on the plywood floor that is about 10′ from the stern. Do you think I can cut this bad spot out and replace it with new marine plywood? Any thoughts or suggestions would be most helpful. Thanks

Roger Racine June 24, 2010 at 1:29 am

I have a suntracker 32′ I need new or used pontoon can you tell me where to fine them. Thanks Roger

Mike Treloar July 2, 2010 at 6:05 am

I recently bought a used pontoon and I took it out once and it performed great. I am redesigning the deck. When I brought it home I stopped and my stepson said he thought there was water in the tubes. I inspected the pontoon tubes and there is a little water. I looked for cracks or any access to the tubes and found a couple access set screws on top of the tubes but they were sealed tight. Should there be some liquid in the tubes for any reason? And do you have any suggestions on what to do if this water wasn’t supposed to be there?

Efraim Shapiro July 12, 2010 at 10:49 am

I need to construct a pontoon boat with my men’s team for a race in 7 weeks. After considering commercial grade sonotube ( plastic reinforced) and plastic barrels, I am considering making the pontoons out of a foam/plywood laminate. we need to carry about 2300 lbs ( 8 men plus gear). It will be a pedal-driven paddle wheel boat. Do you have any suggestions as to construction and/or materials resources?

Fred October 5, 2010 at 11:19 am

I bought a 2001 20` Parti Kraft 200ES pontoon with a 50 hp Yamaha motor. The motor appears to be a short shaft. Will I be able to use this setup in saltwater ? I am concerned abt. the bouyance of the saltwater raising the prop too far up, out of the water. Thanks.

Mike Gergely December 6, 2010 at 4:19 pm

I live (5 1/2 months per year) in Fort Myers, Florida. Do you know of any companies around here that manufactures just the pontoons (and perhaps the deck) that I could finish myself? I am thinking of a small 16 to 17 foot length, that would fit in the garage.


Terry June 11, 2011 at 4:20 am

Am looking making a big pontoon boat . As big as a foot ball field and would like a recommendation on a power plant or plants to move this in the water

Leave a Comment

Previous post:

Next post: