Fitting a Trailer to a Pontoon Boat

Choosing the right size trailer to fit your pontoon boat is a fairly simple matter but it’s amazing how often people, including marine industry professionals, get it wrong. Logic would dictate that if you have a 20’ pontoon you’d want a 20’ trailer. 24’ pontoon, 24’ trailer, etc. But you must be careful.

Most trailer manufacturers classify their trailers by boat size. PT-20/13, WFB-120/10, PTB-2023-10, KDP-1820-27, PT-1925 are but a few examples. The first number usually represents the boat length. Another number often indicates the tire size 10”,12”, 13”. Another may represent the carrying capacity: 23-2300 lbs., 25-2500 lbs., 27-2700 lbs. The five trailers listed above are about 23’-25’ length overall. The KDP trailer fits boats 18’ to 20’ and most of the trailers above could fit a boat 18’ to about 21’ in length.

You need a trailer longer than the boat to allow enough swing radius in a tight turn. The front of a 20’ pontoon tube could hit the back of the tow vehicle in a tight turn on a trailer that was only 20’ long. Trailers for every size pontoon should be 3’ to 4’ longer than the pontoon boat. A trailer for a 20’ boat should be 23’-24’. A trailer for a 24’ should be 27’-28’ length overall.
properly fit a pontoon boat to a trailer
In the photo to the left, the bunk could perhaps be a few inches longer, but with the weight in the back it’s immaterial.

Different manufacturers use various lengths of carpeted boards to support pontoons. These are often called bunks. Most trailers for 20’ pontoons have bunks 14’ to 18’ in length. That’s because the nose cone on pontoons angle up, like the bow of a canoe. They cannot be supported beyond the point where they start to angle up. There is no benefit to longer boards because of the nose cone and also because all the weight is in the stern.
fitting a pontoon trailer

The way the trailer fits in the back is more critical. Most of the weight in modern pontoons is in the stern. The captain’s helm, gas tanks, the engine, etc. The back of the tubes should not extend much more than a foot beyond the back of the trailer. The images to the left show a good fit. The image on the far right shows a boat with 3+’ of overhang. This will affect the balance on the trailer and result in too little tongue weight. In the picture you can see how the front of the trailer seems tilted up.

Our trailers are fully adjustable. Older boats were 8’ wide and are usually on 72” centers. Newer boats (after about 2008) are often 8’6” wide and are usually adjusted to 77” centers. But there is no exact dimension for all brands. The rule of thumb is 72” and 77” but for a perfect fit you should measure the center to center distance. It’s just a ten minute job to move the carpeted bunks, but its easier to do with power tools at the manufacturer or dealership.
Adjusting a pontoon trailer
It’s possible to use some trailers for various length pontoons. By sliding the winch stand forward or back you have about 2’ of adjustability. The same trailer frame can fit a 18-21’ or 22’-24’ boat. You must be careful when moving the winch stand back to make sure you maintain proper tongue weight.
fitting your pontoon trailer to your boat
The strength of the winch stand is in the center of the support arms. The front of the pontoon should rest as closely to the center as possible. These front arms take considerable force when you come in fast. This is called power loading. On a good ramp you drive your boat all the way onto the trailer. If you don’t throttle back you can actually damage the winch stand and the front of the boat. Newer boats have larger diameter pontoons. Some trailer manufacturers still use winch stands designed for 23” diameter pontoons on 25” or 27” diameter pontoons. Make sure the winch stand is the proper height for your pontoons. Most manufacturers won’t offer you any warranty relief if you damage their stand. In our opinion companies that use short stands on big pontoons have a design defect, but again it will be your problem, not the trailer builder.
Below is an example of a poorly fitted trailer.
trailer does not fit pontoon
Unfortunately it's one we sold. The customer told us he had a 23’ pontoon and we set up the trailer to fit. Unfortunately when he got the boat on the trailer he discovered his pontoon was a 20’ pontoon. Fortunately he was only a couple hours away and we were able to swap out trailers, but this is an example of why getting the proper information allows us to help you achieve a perfect fit. 
The pontoon below is the deluxe Bennington Q series on a custom 6” frame trailer. The owner didn’t scrimp on this package. The trailer is extremely well made and braced, BUT the trailer is 8’-10’ too long for the boat. It’s a triple axle so weight distribution probably isn’t a problem, but it seems that the selling dealer or the customer might have noticed all the trailer sticking out the front. When traveling with a 27’ long pontoon an extra 10’ sticking out the front just seems wrong.

The trailer has a Bennington sticker on it, to match the boat. Bennington did not make the trailer the dealer added the sticker. If the owner needs warranty or parts when he calls Bennington he’ll find out they didn’t make the trailer. Hopefully the trailer manufacturers name will be on the original bill of sale. I’m not a “fan” of white trailers, they show dirt easily and sooner or later you’ll see small rust spots, but it does match the white fiberglass front of the pontoon and looks gorgeous at least when its new.
improper fitting pontoon trailer improper fitting pontoon trailer

Here’s another trailer that’s too long, it’s for a Quest 14’ pontoon that’s closer to 12’ long. The boat is on a trailer designed to fit a 14’-16’ pontoon. The customer probably ordered a 14’ trailer only to discover his boat was shorter.

On a small boat like this having a bit of extra trailer in the front can make launching easier. Because the boat is lightweight, balance won’t be a problem.

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