Do it Yourself Trailer Surge Brakes

If you’re new to trailer sailing, you might be unsure about your trailer’s brake system (or lack thereof). If you own an older trailer, the system could be badly corroded from many wet launches and need repair or replacement. If your trailer doesn’t have a brake system, you might be wondering why and if you should have one. This post gives you the facts you need to trailer safely and legally.

My original trailer for Summer Dance had hydraulic surge brakes when it was new but those were eaten away by salt water at the time when I bought the boat. The replacement trailer had no brakes at all.

My tow vehicle is a 1998 Toyota Tacoma Extra Cab 4×4 with a 3.4 liter V6 (190 hp) engine. Including its fiberglass canopy, it weighs in at an even 4,000 pounds. Our 1984 Calkins trailer and 1981 C-22, not including the outboard motor, fuel, water, and other gear weighs around 3,200 pounds. If you have a public, solid waste transfer station in your area, you might be able to weigh your boat for free like I did when we lived in Washington state.

The Washington State Patrol Inspection and Trailer Requirements specify that all trailers exceeding 3,000 pounds or 40% of the tow vehicle weight must have brakes, so ours qualified on both points. Our typical load is more than 200 pounds above the maximum allowable weight and it is also 80% of the tow vehicle weight, double the allowance. Plus, it’s just common sense to not expect to be able to slow or stop a load of that size without an additional braking system.

When your towed load is a small percentage of the towing vehicle weight, the weight of the vehicle helps to control the weight of the load around corners and when braking. When the towed load is a high percentage of the weight of the towing vehicle, it can be the opposite. The weight of the load can overcome the weight of the vehicle in corners and when braking, resulting in understeer and oversteer (what truck drivers call jack-knife). Without trailer brakes, if you are involved in any kind of traffic accident, not the least of which could be rear-ending a vehicle in front of you, you could be held liable due to negligence if you have not met your state’s trailer requirements.

What happens when you don't wash salt water out of your brakes.
What happens when you don’t wash salt water out of your brakes.

I chose to add a complete, new surge brake system to my trailer. It wasn’t particularly difficult, the parts were easy to buy, and it made towing Summer Dance much more relaxing and safer.

Design considerations

Surge brake systems are relatively simple and effective. That’s the good news. The design choices are few: drum type or caliper type. Drum type systems are slightly lower cost and strong enough for most trailerable sailboats, so that’s what I chose. But the tongue extension of our trailer posed a couple of uncommon build challenges. First, the tongue extension is a 2-1/2″ square tube but surge brake actuators are only available in 3″ or larger sizes. Second, I need to be able to disconnect the hydraulic line at the actuator to extend the tongue for launching and then reconnect it for towing.

Bargain shopping

Parts for these systems have standard sizes and have been around for a long time, which means suppliers are many and prices are competitive. More good news. I compared prices from both local and online suppliers. I try to buy local when the cost difference is negligible or service after the sale is important. Local discount suppliers had reasonable prices, especially when shipping costs (nearly $100 at the time) are added to online prices.

But if you can find a free shipping promotion like I did, the savings makes a big difference. I settled on All the major parts came to less than $400 delivered:

  • Demco actuator with breakaway lock
  • Dexter drums
  • Demco galvanized free-backing assemblies
  • Hydraulic line kit
  • New bearings and seals

Delivery was fast and the packaging was excellent. Bob Gisi at was prompt when I requested a technical review of my order before shipment and he was very helpful when replying to installation questions by email. I can recommend them without hesitation.


Except for the challenges mentioned above, the installation was pretty straightforward. The trailer axle already had mounting flanges and the brake assemblies bolted right on. The drums and bearings were direct replacements for the old brake-less hubs. Other than a dog fight drilling a hole in the axle to mount the hydraulic line tee, the pre-cut and pre-flared steel lines were easy to route through existing holes in the frame to the tongue.

Steel hydraulic exiting the frame on its way to the axle tee. The hose allows axle movement.
Steel hydraulic line exiting the frame on its way to the axle tee. The hose allows for vertical axle movement.

I secured the lines to the outside of the axle with stainless steels ties hoping they will last longer than plastic, but they didn’t tighten as well as I had hoped. You can also secure them with U straps and screws if you want to drill more holes in the axle.

Right wheel. Extra tubing is rolled into a coil.
Right wheel. Extra tubing is rolled into a coil to provide vibration relief.

Biting my tongue over the tongue

It’s at the tongue where I got to (had to) be creative. As I said before, the actuator didn’t fit the tongue extension and the hydraulic line needed to be disconnectable. If your trailer doesn’t have a tongue extension like mine, then you should be able to get an actuator that fits your tongue perfectly and you can connect the hydraulic line directly to the actuator.

I solved the first challenge by installing two 1/4″ thick spring shackles as shims between the actuator’s 3″ wide mounting flanges and the 2-1/2″ wide tongue. The shackle holes were almost perfectly spaced out of the package but required slight resizing. I made a couple of 2-1/4″ long spacers out of 1/2″ steel pipe to reinforce the inside of the tongue tube so that I could torque down the actuator mounting bolts through all four pieces.

I solved the hydraulic line problem by installing a quick disconnect fitting between the actuator and the steel hydraulic line. These are the same kind of fittings used for portable pressure washer hoses. Choose brass fittings so they won’t rust. Mine required 1/8″ to 1/4″ adapters on both sides of the fitting.

I inserted a short brake hose between the quick disconnect fitting and the steel line and secured the end of the steel line to the frame with a handmade bracket. The result is that I can easily disconnect the brake line along with the lights before launching and reconnect them before hitting the road. I’m pleased that this doesn’t introduce air into the system and doesn’t affect braking.

Quick disconnect hydraulic line to the new Demco actuator.

After all the hardware is installed, all that remains is to fill the reservoir with fluid, bleed air from the lines, adjust the brake shoes, and road test. The installation instructions cover each of these steps.

The new setup is much easier to stop now. Besides being safer, it also makes trailering a more relaxing experience, which is especially important on longer trips.

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9 Comments Add yours

  1. S/V G'Day says:

    Have you had any problems with the quick disconnect part of the system since you installed this?

    1. I will probably replace the O ring seal inside the female coupler soon but other than that, none.

      1. Lane says:

        Im in the process of looking for a used 30′ + sailboat somewhere in california the problem is i live i canada.I have so many question to ask as i am new to sailboats

      2. Welcome to sailing, Lane!
        Did you look in the Seattle area? Some nice boats can be had there, albeit at a little higher prices than CA. But it would save you a lot of time and transportation costs.
        Read everything you can, watch YouTube videos, find a local mentor if you can, and practice yourself. If you have questions about any of the topics on this site, feel free to ask a question in the comments and somebody will reply.

  2. Ed in Gig Harbor says:

    Have you looked into electronic brakes and use of a brake controller, as opposed to surge systems? I wonder if there is a point where one is a better choice over the other. My Ford F150 has the towing package that made installing the controller easy and we use it for towing our 2200# travel trailer. I am hoping to convert my EZ Loader/ Venture 21 boat trailer and save running all the hydraulic lines (and avoiding that disconnect challenge, if I were ever to rig a tongue extension).

    Thanks for reporting on another useful project is a very thoughtful and helpful way!


    1. Hi, Ed

      Yes, I did consider electric brakes and electric over hydraulic (EOH) systems before I decided on a surge brake system. The general consensus among boat trailer owners is that submerging electromagnetic brakes and their wiring in water isn’t a good thing, as this West Advisor article states:

      RV-grade systems, with painted automotive-grade components, are not intended for submersion, especially in salt water. Submerging a pair of electromagnet actuators and their wiring is generally regarded with the suspicion that occurs whenever you mix water with electricity. One of our suppliers (Cequent Performance Products) does make marine-grade electric brakes. Tie Down Engineering does not recommend their electric brakes for marine applications.

      EOH system are a much better choice because they use the same hydraulic components as surge systems do except instead of a mechanical hydraulic actuator, they employ a motorized actuator controlled from the cab. The biggest drawback is the much higher cost, typically more than the cost of most entire boat trailers, as this BoatUS article states:

      The downside to EOH is cost: While the price has dropped over recent years, it’s still in the $2,000-$3,000 neighborhood to make the change, depending on truck, trailer, and brake manufacturer.

      Still, you’ll probably be submerging the EOH controller at every launch and retrieval. Since you already have a controller installed, an EOH system might not be a bad option for you and definitely worth comparing the pros and cons with a surge system before deciding.

      Read over both the articles I linked to and see what makes the best sense to you.

      1. Ed Bachmann says:

        As is typical, your reply is thoughtful presented, we’ll reasoned and thoroughly supported. I’ve just added another project to my list! Thanks for sharing your wisdom and amazing store of knowledge in this sailing blog.

  3. Lee says:

    Is there any reason to use a hydraulic coupler with manual lockout over electric lockout? I’m planning on replacing old rusty drum brakes with hydraulic disc brakes and use Titan coupler with electric lockout. Thanks!

    1. Just the extra wiring complexity and risk of corrosion and shorts from being immersed.

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