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How to Properly Adjust the Bunks on a Boat Trailer

Written by J. Harvey / Fact checked by S. Numbers

how to properly adjust the bunks on a boat trailer

Adjusting boat trailer bunks is essential to carry the boat’s load correctly. When doing so, you also have to include the PVC, plastic, or carpet adjustable boat trailer skids where the boat rests.

Plastic bunks are usually for aluminum vessels, and they have a longer life span. The carpet bunks need replacement from time to time. To make the adjustments, you have to check the keel rollers carrying most of the boat’s weight and bunk brackets.

There will be no wobbling when you know how to properly adjust the bunks on a boat trailer. To make sure you’re adjusting the bunk of your boat trailer correctly, read on.

Reasons To Adjust The Bunk On A Boat Trailer

There are several reasons why you have to adjust boat trailer bunks to match your boat’s hull.

  • Be aware that new boat trailers produced by major manufacturers are typically from the production line when buying them together with a new boat from a dealer.

This context means that boat trailers from a specific manufacturer are all made the same before being sent to a dealer or boat builder. Most dealers don’t spend time checking the products for the customers as they only think of profits.

  • Adjustments are also essential when you want to upgrade or replace the bunk on your boat trailer. There will be some instances that the one you bought doesn’t fit on your trailer.
  • Vice versa, you may already have a boat trailer that you intend to use for your new boat. You’re only lucky if they perfectly match without needing adjustments.

Proper Ways To Adjust The Bunk On A Boat Trailer


When you find yourself in the above-mentioned situations, don’t ignore the importance of making adjustments on the boat trailer bunks and the brackets. It’s indispensable for a setup that matches your boat’s hull.

Once your boat is in the right sitting position on the trailer, a smooth ride is guaranteed. Easy retrieval and launching also follow. If there are keel rollers on the trailer, the boat’s load can be evenly distributed on them. This is a must for safety. Know and keep in mind the following tools and steps.

What You Need:

  • Adjustable wrench
  • Screwdriver
  • Torque wrench

Step 1. Checking the Keel Rollers on the Boat Trailer

Checking the keel rollers present on your boat trailer is the very first step because you have to find out if your boat rests on them or not. 70 percent of the boat’s weight is contained on the keels. You now have the idea that they support and stabilize your boat.

To be sure that your boat rests on the keel properly, climb or place yourself under the trailer. It’s the easiest way, but if not, you have to do it the other way. You have to go under and use a wrench to loosen the brackets.

Move up the brackets for your boat to rest on the keels. You better start at the front part and up to the rear. It may sometimes be difficult to go under your boat when placed on the trailer. When it happens, you may remove your boat or make the rollers higher.

Know the amount of space and limitation when raising the brackets. The rollers situated in the front of the trailer are a tad higher than the ones in the rear. This should be followed all the time for easier launch at a boat ramp and to adapt to the shape of the boat’s keel.

Step 2. Making the Adjustments

You can begin with the necessary adjustments after the keels are placed correctly on the rollers of the boat trailer. At this point, the boat sits well on the keel rollers. In this setup, it’s uncomplicated to make some changes even without removing your boat from the trailer.

Various bunks are for boat manufacturers to use. Nevertheless, there’s a general guide. The trailer bunks should be resting about 1/3 from the bottom part of the boat’s hull. This step requires you to start in the front of the boat trailer.

Raise the brackets by loosening them so the bunks will lie on the boat’s hull. After you made the front section recline on the bunk guide, you have to do the same process on the rear bunk brackets. The same procedures should be done on both sides of the boat.

You’ll know that you did the proper steps if your boat isn’t tipsy but instead, sitting well on the entire bunk and keel rollers (if your trailer has them). However, if your vessel is unsteady, you have to redo the previous steps.

Determine which part makes your boat wobbly or unstable. You have to adjust brackets if needed.

Things You Have To Pay Attention To When Adjusting The Bunk


  • Transducers

You have to place the trailer bunks in a firm position when you have a transom-mount or thru-hull transducer. They don’t need to be in contact with the transducer. In rare cases, transducers are moved out to give way to the boat trailer for the right fitness.

If you don’t handle the transducer well, it will likely get damaged, including the trailer.

  • Bow Pulpit

This is a narrow platform that goes all the way to the boat’s front. A bow pulpit can be cosmetic and functional. It usually gives support and extension to an anchor davit. This accessory needs support whether the boat is unloaded or loaded.

In moments that the hull disconnects from the trailer when sliding into the water without the right timing, the pulpit may hit the winch stand. The good news is that you mend this circumstance through bow guide boards.

  • Inboard Engine

Two kinds of inboard engine configurations go along with trailer fit. They’re V drive and straight shaft. The first one is optional and placed on the trailer’s rear. It provides support for the extra weight from the engine, similar to a stern drive configuration.

The second type has two main functions. It pushes the engine forward to the front and helps the trailer’s axle position to gain proper tongue weight.

Tips And Precautions

  • As a responsible boat owner, you have to keep all the parts and accessories in their optimum performance. The bunks of the boat trailer are one of them. So, always check their stability.
  • Keep your fingers away from the space between the boat and the bunks. Even though most of the boat’s weight is supported by keel rollers, never do it when you work on adjustments or set up boat trailer bunks.
  • You can’t always avoid bumps and potholes , which can loosen up bunks and keel rollers. These are just some reasons why constant bunk adjustment is vital. It’s a way to prevent injury, damage, and lowering of performance.

Takeaway With Bunk Adjustments

Include the procedures on how to properly adjust the bunks on a boat trailer as a part of your boat maintenance. Whether you have a new trailer or boat, it’s one of the important things you have to take care of.

Do it regularly as you don’t always pass at a clear and bump-free road. The bunk would probably be moved. Always remember to make your boat stable on the trailer by making bunk adjustments.

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