Boat Trailer Maintenance Priorities: What to Fix First

If you’re buying a new or used boat under 30 feet, chances are, the boat you buy will be sitting on a trailer. Odds are good that any money the previous owner spent to make the boat more appealing was not spent on the trailer, as this aspect of boat ownership and boat maintenance is often be overlooked. That means if you want to be sure you get your boat to the water, you should give the trailer a good once-over before heading out.

Good news: boat trailers aren’t complex, so trailer maintenance — even when deferred by a previous owner — is usually straight-forward and hopefully won’t eat up too much of your annual boat budget costs. The systems that need regular maintenance are, in order of importance: brakes, hubs and bearings, leaf springs, axles, couplers/connections, bunks, jacks and electrical components (including your operational driving lights). Let’s take a look at them one at a time.

Trailer Brakes: Vital Safety Equipment For Larger Trailers

When replacing items like brakes or lighting, spend a little extra and get good components. Photo courtesy of West Marine.

Above: When replacing items like brakes or lighting, spend a little extra and get good components. Photo via West Marine.

Smaller boat trailers often do not have brakes, and instead stop thanks to the towing vehicles braking power. Larger trailers for boats between 20-30 feet will often have their own brakes and these should be checked at least twice a year: in the spring, at the beginning of the boating season and at the end of the boating season, in the fall, when it is time to put your vessel in storage for the winter (unless you live somewhere where you can boat year round of course). It’s wise to check them a few more times throughout the year as well, particularly if you are using them a lot in saltwater bodies of water.

With regular flushing, a year and a half is about the average lifespan for a set of drum brakes used in salt water, so if the previous owner was lackadaisical about flushing, plan on replacing the assemblies. Go for the whole shebang, which includes shoes, backing plates, hardware, and wheel cylinders. It sounds expensive, but it’s not. Boat trailer brake assemblies usually come assembled, so all you have to do is bolt them on, making the process much easier.

If you have the brake drums and hubs off, you’ll be into the bearings. These can be the biggest headache of all if you don’t service them, and they are usually the reason you see boat trailers stranded by the roadside, so let’s get to that next.

Hubs And Bearings

Bad hubs and faulty bearings are a major safety concern. Ever been on the road and see a trailer pulled off to the side with a wheel sitting at an angle and a boat slumped over to one side? That’s what happens when a hub fails – the wheel can fall off completely, or become partially detached, and render the trailer in-operable, risking the safety of you and those around you on public roads, not to mention damaging the vessel itself.

Using a flat head screw driver, carefully pry off the dust caps (the center caps in the middle of the wheels) in order to inspect the bearings. Remove excess grease and clean inside the bearings with an approved bearing cleaner solvent. Inspect the bearings and if they are rusted, scored or pitted, it is time to replace them. Luckily, new bearings for a boat trailer are relatively cheap. To install new bearings, take a glob of grease and put it on the inside of the bearing, then seat the bearing where the previous bearings were and use a rubber mallet and punch to hammer them into place, rotating the bearing as you get it lodged in place. A bearing packer will make this job much easier and is highly recommended. Coat the outer edge of the bearing seal with sealant and make sure everything is mounted flush. Now it is time to tight the trailer hub castle nut. There are various methods of doing this but it is somewhat similar to tightening a lug nut on wheels. Make sure it is seated properly and there is no wobbling. Be careful not to over-tighten, as this can damage the bearings. Essentially the bearings should be turning freely while also being securely fastened in place.

Most likely you have cone and cup bearings. If that’s the case, be sure you have a set of stainless steel Bearing Buddy caps installed. A Bearing Buddy will keep water out, but it also will tell you immediately when your bearings are low on grease. If the outer spring is compressed, they’re full. If the spring is extended, add grease till the spring compresses fully. Regardless of how often you top them off, pull them apart at least once a year and clean, inspect, and repack them with fresh grease and always, always use new seals.

Leaf Springs

First and foremost, if you’re using the boat trailer in saltwater the entire trailer, and specifically the leaf springs, should be rinsed after every use to prevent saltwater from corroding the leaf springs. If maintained properly, leaf springs can last 5-10 years, but if not, they can last only a season or two. Another way to extend way the life of your leaf springs is to apply water repellent coating and rust inhibitor solvents regularly.

Trailer Axles

The axle(s) on your trailer support the entire boat on the road, thus are imperative. If the axles are rusting out, or look dented, bent, scored or “pitted” it is time to replace the axle. Faulty axles are a major cause of trailer failure and a serious safety concern.

Couplers And Connections

Check all connections, including hooks, winch, trailer ball and safety chains. They should be free of rust and solid. Be sure the coupler latch moves the collar that locks under the hitch ball. Also, look up into the coupler to inspect wear. Though it is rare, hitch balls have actually worn through the top of the coupler, so be sure the coupler stays greased. Do it the easy way, without getting your hands dirty: Two or three times a year, simply turn a tub of grease upside down and lower it onto the trailer ball. Grease will stick to the ball, which will lube the trailer coupler when you hook it up. Shoot some penetrating lubricant, such as WD-40, into the moving parts.

The tongue jack also needs lubrication. Many of them have a grease fitting for the rack and pinion inside. If your jack has a lock pin with a spring-loaded ball, shoot some penetrating lubricant on it, too.

Trailer Bunks

For bunks, it’s also largely a matter of inspection. As for lubricating the bunks, it’s largely unnecessary. You do need to be sure the carpeting that covers them is in good shape and that the wood the carpeting is stapled to is sound. Inspect the carpet to see if there are any tears in it that would expose the wooden bunks. If so, replace the carpet. Bunk carpeting can tear a bit more frequently on trailers that carry stepped-bottom boats, because the steps rub the material as the boat slides up and over the forward edges of the bunks.

Electrical Systems

Now let’s talk electrical. First, see if all your lights are working. Then have someone step on the brake pedal and actuate the turn signals to see that they work. As you can see, much of the maintenance involved in electrical systems is a mere matter of inspecting them. Also, be sure to inspect the rubber grommets where wiring enters and exits the frame. If they’ve fallen out or rotted away, your wires can chafe and ground out. If you do have to replace any of the lamps, spring for sealed LEDs, which are more reliable because there are no incandescent bulbs to fail.

A lot of maintaining a trailer is paying attention to it on the days you use it. When launching, look at the bunks. When hooking it up, check the coupler, and check the lights each time you go out. Maintaining a trailer isn’t fun, but doing it right means you get to the water every time. And that is fun. 

Written by: Ryan McVinney

C. Ryan McVinney is a film director, producer, writer, actor, boat captain, outdoor enthusiast and conservationist. He's currently the host and director of Boat Trader's Stomping Grounds TV show that explores boating culture across America. McVinney produces the Cult Classics video series for YachtWorld and the Factory Fridays show for and is a regular contributor to leading marine industry publications.