How to Grease Boat Trailer Bearings: A Step-by-Step Guide for Smooth Towing

Regular bearing maintenance prevents costly breakdowns and keeps you moving safely on your way to your favorite waters.

Learn how to grease and maintain your boat trailer bearings with this step-by-step guide. Enjoy your time on the lake instead of wasting your time on the shoulder of the highway. | Photo by Kurt Mazurek

Why Greasing Boat Trailer Bearings Matters

Boat trailer bearings failing on the highway can ruin a fishing trip. But they can also put you in a really unsafe situation. Maintaining them is quick, easy, and something every boat owner should learn to do.

The following steps apply to most standard unsealed bearing hubs which are common on lots of boat trailers, but there are some exceptions. Double check your owners manual to confirm which style of hubs are on your trailer.

What You’ll Need to Grease Boat Trailer Bearings

• Jack
• Lug wrench
• Marine-grade grease
• Hammer
• Pliers
• Flat screwdriver
• Wood block
• Brake cleaner spray
• Shop rags

Step-by-Step: How to Grease Boat Trailer Bearings

Step 1. Remove Lug Nuts

Begin re-greasing your trailer bearings by removing the lugs with a lug wrench. | Joe Shead

Just like changing a flat tire, start by cracking loose your lug nuts while the tire is still on the ground. Once loose, slide a jack under the axle and raise the tire off the ground. Continue removing the lug nuts and remove the tire.

Step 2. Remove Wheel Bearing Cap

To remove the bearing cap, hit the corner at an angle with a hammer, then spin the wheel a half turn and repeat. | Joe Shead

Remove the bearing cap by lightly tapping it at an angle with a hammer. It should pop out a little. Spin the wheel a half turn and repeat. You can keep spinning and tapping until the cap comes off, or once it's started, stick a flat screwdriver in the gap you've created and pry it off.

Once you've created a gap behind the bearing cap, you can pry it off the rest of the way with a flat screwdriver. | Joe Shead

Step 3. Remove Cotter Pin and Castle Nut

Straighten the bent end of the cotter pin that holds on the castle nut with a pliers, then pull the pin through the castle nut at the rounded end. | Joe Shead

A cotter pin keeps the castle nut from loosening. First, straighten the bent end of the cotter pin with a pliers (it's bent so it fits inside the bearing cap.) Then insert a pliers inside the rounded end of the pin and pull it out. With the cotter pin removed, unscrew the castle nut and remove the washer behind it.

With the cotter pin removed, unscrew the castle nut and remove the washer behind it. | Joe Shead

Step 4. Take Out and Clean Outer Bearing

Remove the outer bearing. | Joe Shead

Slide out the outer bearing. Using brake cleaner, spray the bearing to remove old grease. Spray and wipe until the bearing is completely free of grease. Inspect bearing for damage. If it's worn, replace it.

Use brake cleaner to spray old grease off the bearings. | Joe Shead

Step 5. Slide Out Hub

With the hub raised off the ground between two blocks, I use an old window weight to pound against a small wood block to punch out the inner bearing and seal. | Joe Shead

Slide out the hub to get at the inner bearing. Rest the hub with the inner bearing pointing down between two blocks. Position the bearing over the gap between the blocks so you can pound it out. Find a dowel or similar block of wood (use wood, which has some give. Using something rigid like metal could damage the bearing) that is narrow enough to slide in the hub, but wider than the bearing. I cut a block to shape with trial and error and now keep it with my bearing grease for this one specific job.

With the wooden dowel over the bearing, pound it out with a hammer. Detach the bearing from the inner seal and clean both with brake cleaner.

Slide the hub off the shaft and place it over two blocks with a gap in the center, which allows you to pound out the inner bearing. Use a dowel or block of wood narrow enough to fit inside the hub, but wider than the inner bearing. Pounding on wood instead of pounding directly on the bearing prevents damage. In this picture, I use a specially cut wood block (left) and pound on it with an old window weight (bottom) which fits nicely inside the hub. | Joe Shead

Step 6. Re-Lube Bearings

A bearing with new grease, ready to keep on rolling. | Joe Shead

With both inner and outer bearings completely cleaned of grease, pack them with new marine-grade grease, which is resistant to water. You can put them in a special bearing packer, which jams grease into the bearing, or do it by hand. Work the grease into every gap around each bearing. Better to use too much grease than too little. At every point in the process, only let the bearings come in contact with clean surfaces if you set them down. Don't let dirt or other debris get inside the bearings!

Step 7. Replace Inner Bearing and Seal

Reinstalling the inner bearing and seal. A block of wood prevents damage when pounded back into place. | Joe Shead

Inspect the bearing and seal for damage. If they are in good condition, you can re-use them. Otherwise replace them. Place the greased inner bearing back in the inside of the hub. Place the seal over the top. Put a block of wood over the seal and squarely hit the wood block with a hammer to seat the bearing and seal.

Step 8. Grease the Spindle

Apply a generous amount of grease to the spindle shaft. | Joe Shead

Apply a generous amount of grease to the spindle. Then slide the hub onto the spindle.

Slide the hub assembly (with inner bearing and seal in place) back on the spindle. | Joe Shead

Step 9. Replace the Outer Bearing, Washer and Castle Nut

Slide the outer bearing onto the spindle. Add the washer and castle nut. | Joe Shead

Slide the outer bearing onto the greased spindle. Make sure it goes on all the way. Add the washer. Then replace the castle nut. Screw the castle nut on by hand all the way, then back it off one notch so the bearings can spin freely. Insert the cotter pin back through the notch and bend the end so it stays inside the bearing cap

Hand tighten the castle nut, then back it off one notch. Push the cotter pin back through the hole and bend the ends of the pin so they stay within the bearing cap. | Joe Shead

Step 10. Replace the Bearing Cap

Add the bearing cap. Use a block of wood to prevent damage when tapped squarely back into place. | Joe Shead

Pound on the bearing cap with a piece of wood between the hammer and the bearing cap to avoid damage. Hit it squarely so it seats flush.

Step 11. Replace Tire and Tighten Lugs

Mount the wheel and tighten the lug nuts. | Joe Shead

Put the tire back on the hub and tighten the lug nuts. Lower the jack and when the tire is on the ground (keeping the tire from spinning) further tighten the lug nuts

Don’t Let a Bad Bearing Ruin a Perfect Fishing Day

A blown trailer bearing can turn what was supposed to be a great day on the water into a long, exhausting roadside repair. This quick, easy, inexpensive DIY routine, performed at least once per year will keep your trailer road-ready and your focus on your fishing.