Grease your boat trailer wheel bearings once a year as part of your annual boat trailer maintenance program. Learn how to grease boat trailer wheel bearings in this easy-to-follow step-by-step narrative, along with our at-a-glance quick guide.
Greasing trailer wheel bearings is not difficult to do, but it is an essential trailer maintenance item because if a wheel bearing fails, the wheel can come off unexpectedly, create an accident, or cause damage to your boat.
It’s easy to overlook this maintenance item because wheel bearings are out of sight. However, repeated submersion in water along with a sandy environment leads to boat trailer wheel bearings needing regular attention.
How To Inspect, Disassemble, and Grease Boat Trailer Wheel Bearings
It’s quite a simple process to maintain the wheel bearings. First, slightly loosen the lug nuts while the trailer is on the ground. Then jack up the trailer, so the wheel is off of the ground.
Ideally, for stability, the trailer hitch is connected to a vehicle, and the opposite wheel is chocked. A jack stand adds further security and safety.
Next, give the wheel a spin. Does it turn freely without a grinding sound? Then grab the wheel and firmly shake it from side to side. Is there any wobble and play in the bearing? Ideally, there is very little play.
If the wheel wobbles when you shake it, then it’s likely you actually need to replace the bearings and races. If you are mechanically handy, this is a straightforward job. However, if you’re not mechanically confident, take it to a shop or use Trailers and Transport [mobile trailer service].
Next, remove the wheel. Now you can inspect the hub for integrity and look inside of the rim to see if there’s been grease escaping. If grease has been escaping from the seal, that means water and contaminants can get in and degrade the bearings.
Next, pop off the dust cap with a mallet by knocking it equally from side to side. Once the cap is removed, this exposes the axel nut that holds the hub and the cotter pin that secures the nut in place. Remove the cotter pin. Remove the nut. Remove the large washer. Inspect for any metal shavings, debris, water, or contaminants.
Next pull the hub toward you and remove the outer bearing. Leave the wheel on the spindle. Wipe the outer bearing with a clean rag and inspect the bearing for any rust, pitting, or any deformities on each of the roller bearings. Ideally, it’s smooth, clean, and does not need to be replaced.
If you see rust, pitting, or deformities, then the bearings and races are due to be replaced.
Next, here’s a little trick. With the wheel still sitting on the spindle, put the axel nut back on. Pull the hub toward you fully, and it will pop out the inner bearing and the seal when it catches the nut. Inspect and clean out the inside of the hub looking for metal shavings or any sign of degradation.
Wipe the inner bearing and the seal clean while inspecting both for integrity. The seal is double-lipped to keep the grease in and water out.
At this point, let’s assume the bearings are in good shape, the seal has integrity, and the races that the bearings ride on inside the hub are also free of pits, rust, and deformities. Clean the spindle and inspect that it too is perfectly clean and smooth.
With everything wiped clean it’s time to press fresh marine-grade grease into the bearings and begin reassembly. Use a gloved hand with a good-sized glob of grease, take the inner bearing and scrape it against the glob and use pressure to press the grease throughout the bearing.
Keep rotating the bearing while pressing in grease until it emerges on both sides. Wipe a little excess grease on the race and the seal and place the inner bearing into the race and tap the seal in gently with a hammer or mallet until it is fully seated.
Now repeat the process to press grease into the outer wheel bearing. Place the hub on the spindle, then place the freshly greased outer bearing into the outer race. Next, replace the large washer and the nut.
At this point we want to adjust the tightness of the nut to limit excess pressure on the wheel bearings. Use a wrench or adjustable channel lock pliers to tighten the nut fully. This snugs up the seal and the bearings onto the races. Then back off the nut slightly and then re-tighten the nut by hand. Replace the cotter pin and dust cap.
Put the tire back on and tighten the lug nuts. Spin the wheel. It should spin freely and quietly. There should be no wobble in the wheel when you shake it. Lower the tire to the ground and fully tighten the lug nuts.
Congratulations! One wheel bearing is greased, now repeat on the other side of the trailer.
Quick Guide to Greasing Boat Trailer Wheel Bearings
- Slightly loosen lug nuts. Jack up the wheel.
- Shake wheel, inspect for wobble.
- Spin wheel. Does it spin smoothly?
- Remove wheel to expose hub.
- Remove dust cap, cotter pin, axle nut, and washer.
- Inspect existing grease for water or debris.
- Pull hub toward you and remove outer bearing.
- Pull hub off and remove seal and inner bearing.
- Wipe all bearings and races clean with a clean rag.
- Inspect bearings and races for rust, pitting, or deformity.
- Clean all surfaces fully.
- Press fresh marine grease into the bearings.
- Insert inside bearing into race and reinstall grease seal.
- Put hub back onto spindle and insert outer bearing.
- Replace the washer and fully tighten nut to seat the parts.
- Back off the nut and then hand tighten.
- Replace the cotter pin and dust cap.
- Replace the wheel and tighten lug nuts.
- Lower wheel to ground and fully tighten lug nuts.
How to Replace Damaged Wheel Bearings
If upon disassembly you discover that the wheel bearings are rusted, pitted, or have some deformities on the roller surfaces, take the sample bearings to the auto parts store or trailer dealership. Purchase new bearings, races, and seals, along with the marine-grade grease.
The only difference in the process from described above is that we need to take a punch and pop out the old inner and outer bearing races. Lay the hub down, and with a long punch, reach through the hub to the opposite side and find the back edge of the race with the punch.
Knock the punch with a hammer alternating opposite sides of the edge of the race to unseat it. Once removed, flip the hub over and repeat the process to remove the opposite race.
Clean the hub fully so there are no metal shavings, dirt, or contaminants. Now it’s time to press in the new races. For this we use a special race driver tool to knock with a hammer. The tool is the same size as the race so that the race can be driven into the hub to its fully seated position.
Once the new races are installed, wipe all surfaces clean. Then grease and reassemble all of the parts as outlined above. As you can see, replacing the wheel bearings really only differs from the basic greasing process by needing to purchase the parts, and replace the bearing races.
A Few Other Spots to Grease on Your Boat Trailer
While you have excess grease handy, grease a few more parts of your trailer so everything functions perfectly.
- Grease the coupler and the latch.
- Grease the winch gears, the release, and the bow clip.
- Grease the trailer jack.
A handy device called a bearing buddy can help keep wheel bearing grease fresh. The unit attaches to the hub where the dust cap would normally be and has a grease zerk. Using spring-action, the bearing buddy presses fresh grease into the wheel bearings over time as required.
Remember, fresh grease displaces water, and water is the enemy because it creates an environment for rust.
Greasing wheel bearings on a boat trailer is important annual maintenance. Not keeping up on this maintenance item will lead to a roadside trailer break down, or worse, your trailer wheel comes off, causing damage to your boat and creating a hazard to others.
It is not difficult to grease your wheel bearings as a DIY project. However, a trailer shop or a mobile trailer repair service like Trailers and Transport can keep all aspects of your boat trailer operating safely and smoothly.