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How To Adjust Boat Trailer Bunks

How To Adjust Boat Trailer Bunks
November 15, 2017 Ultra High

How To Adjust Boat Trailer Bunks | Carpet & Plastic Boat Bunk Guides

Over­time many boat own­ers in Amer­i­ca will come to the point that they will need to either replace their exist­ing boat trail­er bunks or repair their exist­ing bunk guides due to con­stant wear and tear. If you own car­pet bunk guides you will no doubt notice that they con­stant­ly need replac­ing much faster than plas­tic boat trail­er bunks. 

Car­pet boat trail­er bunks are gen­er­al­ly designed for use with fiber­glass hulls. If they are used with alu­mini­um boat hulls, due to the two mate­ri­als clash­ing, this caus­es an unhealthy fric­tion between your boat and bunks which will cause them to rip or tear much faster. Plas­tic boat trail­er bunks on the oth­er hand for alu­mini­um boats last much longer and have a far greater life span and per­for­mance rating. 

In today’s tuto­r­i­al we go over the sim­ple steps on how you can adjust your boat trail­er bunks to make them suit your boats hull. 

Why Do I Need To Adjust My Boat Trailer Bunks?

Plastic-boat-trailer-bunks-12There are numer­ous rea­sons boat trail­er bunks and bunk brack­ets need to be adjust­ed to suit your boats hull.

  1. When you buy a new boat and trail­er from a deal­er, many new boat trail­ers from major man­u­fac­tur­ers are made on a pro­duc­tion line. This means that every boat trail­er from a par­tic­u­lar man­u­fac­tur­er are all made the same before being shipped to a boat builder or deal­er. All the deal­ers are con­cerned about is sell­ing a new boat and trail­er pack­age to the cus­tomer. Rarely do deal­ers put in any work to make sure the boat trail­er has been adjust­ed to suit the cus­tomers new boat. 
  2. If you own a boat already and look­ing at upgrad­ing or replac­ing your exist­ing boat trail­er. The boat trail­er you will look to pur­chase will not be suit­ed to your boat. 
  3. If you own a boat trail­er and look­ing to pur­chase a new boat, your boat trail­er will not be suit­ed to your new boat.

If you fall in to one of the above cat­e­gories, you will need to learn how to adjust your boat trail­er bunks and bunk brack­ets to suit your setup.

By cor­rect­ly adjust­ing your boat trail­er bunks to suit your boat, not only will it sit bet­ter on your trail­er; it will pro­vide a smoother ride while in tran­sit, will help make launch­ing and retriev­ing eas­i­er and if you have keel rollers on your trail­er, the bunks will help to even­ly dis­trib­ute your boats weight on the rollers for a smoother set­up and last­ly, be over­all safer.

Step 1 — Check your boat trailers keel rollers

The first step to ensur­ing your boat is sit­ting cor­rect­ly on your boat trail­er is to check that your boats keel is rest­ing on the keel rollers that may be attached to your boat trailer. 

Approx­i­mate­ly 70% of the boats weight is in the keel, so it is impor­tant that we focus on this area of your boat and that it is well supported.

With your boat on your trail­er, climb or posi­tion your­self as best as pos­si­ble under your trail­er to visu­al­ize that your boat is rest­ing on all the keel rollers. If they are; Great! If not, you will need to climb under and use the appro­pri­ate adjustable wrench to loosen your boat trail­er roller brack­ets and move them up so the keel roller is rest­ing on your boats hull. Start at the front of your trail­er and work your way to the rear.

Note: If you cant get under your boat while its on the trail­er, you will need to launch or remove your boat and then make the adjust­ments of the rollers high­er. Just make note of how much space there is and how much to raise your brack­ets. 

As a gen­er­al guide, the rollers at the front of your trail­er will be slight­ly high­er than the rear rollers. This should fol­low the shape of your boats keel and allow for an eas­i­er launch when at the boat ramp.

Step 2 — Adjusting Your Boat Trailer Bunks

Plastic-boat-trailer-bunks-18Once you are hap­py that your boats keel is rest­ing on your boat trail­ers keel rollers, it is time to make the adjust­ments to your boat trail­er bunk brack­ets and hard­ware. With your boat rest­ing on your keel rollers, you should be able to make changes to your boat trail­er bunks with­out remov­ing the boat from your trailer.

Your boats bunks will vary by boat man­u­fac­ture as to were the trail­er bunk guides will be rest­ing. How­ev­er, as a gen­er­al guide, your trail­er bunks will be rest­ing approx­i­mate­ly 1/3 up from the bot­tom of your boats hull.

Just like your keel rollers, we want to start with the front of your boat trail­er. Loosen your adjustable boat trail­er bunk brack­ets so they are free to raise. Raise your brack­ets so that your bunks are rest­ing on your boats hull. Once the front of your boat is rest­ing on your bunk guide, repeat the same process with the rear bunk bracket.

Once you have fin­ished the first side of your boat you decid­ed to adjust, repeat the same process with the oppo­site side.

When done cor­rect­ly, your boat should not be ‘tip­sy’ and should be rest­ing firm­ly on both boat trail­er bunks as well as your keel rollers. If your boat is still not sit­ting cor­rect­ly, go over your boat trail­er from step 1, and see which part of your boat trail­er is not sit­ting cor­rect­ly with your boat. Adjust your brack­ets as required, so that all boat trail­er parts are rest­ing cor­rect­ly with your boat. 

Tools You May Need

  • Adjustable Wrench.
  • Torque Wrench.
  • Screw­driv­er.


Check the sta­bil­i­ty of your boat trail­er bunks after each time you launch and retrieve your boat. With con­stant use, its not uncom­mon for your brack­ets to shift slight­ly. If this hap­pens, adjust them accord­ing­ly back to their orig­i­nal rest­ing position.

Boat Trailer Bunks



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