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  • Electric over Hydraulic Brake Conversion

    • Year: 2005 Brand: Mastercraft Model / Trim: X-10 Cost: $500-$999

    This year I decided that towing with surge brakes is not my idea of a good time.  Based on that I did some research and settled on electric over hydraulic as the best option for my boat trailer.  Shortly after converting to electric over hydraulic, I decided to buy a new(er) boat.  This time I documented the process so that I could share here.

    Why don't I like surge brakes? 

    1. I don't like the feeling of the trailer sliding when I start and stop while driving.  It just bothers me.
    2. I currently tow behind a truck with a truck camper on board.  The action of the trailer pushing into the truck before it starts slowing down always makes me nervous while towing, especially in turns.
    3. I find them hard to keep adjusted correctly, and most people never do adjust them.  
      1. There is an alarming number of boats traveling down the road with non-functioning surge brakes.
    4. When towing in the mountains of the west, surge brakes tend to be applied the whole time going down hill. This causes everything to heat up and is bad for the bearings.
    5. When loading and unloading at the boat launch, the trailer brakes don't do anything to help the situation.

    What are the benefits of electric over hydraulic?

    1. The brakes are easy to keep adjusted, especially with disc.
    2. The silly shock doesn't wear out every few years ;)
    3. The boat trailer applies brakes only when the truck applies brakes, making for a consistent experience. Even at the boat launch.
    4. On boat trailers, there isn't electricity going to actual brakes under water.
    5. The force applied by the brakes can be adjusted on the road in the truck.

    What are the cons of the electric over hydraulic?

    1. There is a delay between hitting the brakes and the trailer stopping.  This is the time it takes the pump to build pressure.
      1. To be fair, I always found that surge brakes have a delay also.
      2. I also don't find the delay to be an issue.  It's less than half a second.
    2. It's more expensive than other options.
    3. It doesn't work with every tow vehicle on the road.  Requires a brake controller, and the brake controller should be compatible with electric over hydraulic.
    4. Going down hill requires you to apply the brakes more often, because the boat trailer doesn't do it on its own anymore.

    On to the process.

    At a high level the process is to add the EOH controller and pump to the trailer, add a battery breakaway system, wire it up, and then lock out the surge brake coupler.  I'll walk through my steps below.

    These are the parts that will be installed in the conversion:

    EOH actuator, 7 way harness, Breakaway system (battery and switch), rubber brake hose, some grade 8 bolts (5/16" and 1/4").

    optional parts: Wire junction box, Hydrastar CAM.  The CAM depends on your truck, some brake controllers don't support electric over hydraulic. My truck does actually support it but I choose to install it just incase the boat gets towed by a truck that doesn't.


    There are different pressures for different brake systems. This is a 1,600 PSI unit for disc brakes.  If you have drum brakes you will need to research the right pressure from number of axles that have brakes. 

    This is also a marine version of the actuator, it has different seals and stainless internals.

    First step, figure out where everything is going to go on the trailer.  I didn't take a good picture of this, but you'll see my progress.


    Because wires are unsightly, I added some wire loom.  Not mandatory, you choose.  I also always cover my loom in black tape.  This is really because future me likes a sticky mess when working on wires.



    The place I choose for mounting the brake controller has a bit of a step and required me to make a spacer.  I used a little bit of 1/8" aluminum I had laying around.  I can imagine that stacking a couple flat washers would accomplish the same goal.

    cut the spacer to size, mark the holes and drill.  I made the holes in my spacer a little larger than the mounting bracket.  This allowed me to move things around some and make sure they lined up.  I could also compensate for my poor measuring skills that day 😏.  One hole was about 1/16" off.


    Next was to mount, locate and drill and tap (thread) the frame. Be sure you like where it is, this step is rather hard to undo.

    I marked the location of the mounting bracket holes using a 5/16" transfer punch. I Didn't get a good picture of this part.
    Next drill 1/8" holes in all the spots to see if they will work.  Next step up to the right size hole. For a 5/16" bolt, I used a 17/64" drill bit.

    Here is a chart that helps figure out what size hole to make when tapping threads: https://www.lincolnmachine.com/tap_drill_chart.html




    Here is the tapping process.  Take your time on this step.  Go slow and make sure it is straight.  Don't want a broken tap in your hole.  That is mighty inconvenient.


    Here it is mounted in place (sigh, upside down)

    Important side note that applies to these steps.  All of my bolts are installed with flat washers, lock washers, and blue thread locker.  This helps keep the bolts in the trailer frame, but also the thread locker will help seal the holes in the frame to keep water out.


    Next up mount the breakaway battery, wire junction box, and hydrastar CAM.
    The steps are really the same.  Mark, Punch, Drill, Drill, Tap, Bolt,  repeat for each hole.  1/4" tap takes a 13/64" drill bit.

    I mounted the junction box and cam under the trailer to get them out of the way, but also make the wiring more hidden.  Also because I like to cause inconvenient work for future self.





    Next step was to attach the breakaway switch.  The location of this is very important because this is a critical safety component, for the day you forget to fully attach your trailer to the truck. This must be mounted to the furthest point forward that cannot become detached from the trailer frame in case of an emergency.  

    Also, please do not skip adding this to your trailer.  This is a critical safety part for other people on the road.  The last thing any of us wants is a runaway trailer hitting someone on the highway.

    My trailer has a fold away tongue.  This means that it had to be mounted behind the foldaway part, just incase the folding mechanism malfunctions on the highway. I only had one place that the switch fully fit without covering important information about the trailer.

    Steps are the same: Mark, punch, drill, drill, tap, bolt.




    I'm not going to show the pictures, but my next step was to wire loom and and tape everything.  I also took some time to decide on the best way to route the wires to keep them as hidden as possible.

    After that, its time to connect the wiring everything. 

    Be sure to refer to the instructions for your brake controller and brake away system.  They need to be connected in a specific way to function properly. What you see will be specific to the system I'm installing. If your system is different it will likely not be the same.

    There is also a lot of repetition in these steps.  Cut, strip, crimp, shrink, connect.  repeat for each wire and connection.  



    I also connected the 7 pin harness to the truck and adjusted the length at this step.

    For my system these are the connections:

    • White: 12v Negative from truck and trailer frame ground
    • Black: 12v Positive from truck.
    • Blue (brake controller): Trailer brake controller from truck
    • Blue (Hydrastar Cam): Trailer brake controller from truck.
    • Confusing part....  There is a blue wire coming from the breakaway battery.  This is not for trailer brake control. This goes to the the brake away switch.  Both wires on the brake away switch are black.
    • Blue (battery): one side of the brake away switch.
    • Yellow (brake controller): second side of the brake away switch.


    Important part... Make sure your frame is grounding. I like to use a star washer between the frame and the ground wire to help bite into the metal. I don't know if it helps or not, but makes me feel better.


    Next up is to adjust the brake lines:

    I had to disconnect the main brake line at the first brake and pull the line back some.  Then I found my mounting location. I mounted a tab that will be used to attach the rubber brake hose to the frame, this keeps the hard line and flexible line from moving too much while driving. Don't want that hard line to get weakened by extra movement.

    Steps and pictures area little out of order to account for painting time.


    Bend the hard line using a tubing bender.


    Cut the hard line to length using a tubing cutter.


    Double flare the end using a double flaring tool.  (This can be rented / borrowed at most auto parts stores).  Make sure the nut is on the right way before flaring.  That would just be sad.  But practice makes perfect!


    Set the height using the anvil.


    First flare using the anvil


    Remove the anvil and second flare


    Attach them together:

    Not shown,  the other end of the rubber hose goes to the brake actuator.


    Now its time to bleed the system.

    Fill the actuator up with brake fluid.  I used DOT 4 because it is recommended for wet environments over DOT3.

    This my bleeder tool.  Its an old bottle with a hole drilled in the top with some tubing.  I made this thing like 5 years ago and have used it many time times, it needs a new cap.  Put a little bit of brake fluid in the bottle, push the tube into the fluid.  Then the brake system can't suck air back in while you are bleeding.


    Bleed the actuator first (Some actuators don't have bleed ports).

    Turn on the pump by pulling the breakaway switch.  Mine is pretty hard to pull out, probably a good thing, so I rigged up an old switch to the system (which will be removed when I'm done bleeding).

    Run the pump until air stops coming out of the tube. It's easy to see with my setup.  

    Important: do not let the actuator run out of fluid during the bleeding process.  If that happens you will need to start over.  Although... Practice makes perfect.



    Next bleed the brakes.

    Start with the one farthest from the brake actuator.  To figure this out follow your hard lines.  The one with the longest distance of line between the actuator and brake is the farthest one.

    Again, run the pump to push fluid through until no more old fluid or air comes out.  Don't let the actuator run low.  The first one should take longer than the others.

    Repeat for the other brakes.  In my case that was 3 more.


    OK... The Electric over hydraulic actuator is fully setup and installed.  Check the entire system for leaks.

    Be sure to test your brake controller in the truck. Make sure the actuator runs smoothly when the brakes are applied.  It is best to have a buddy help with the step so you can watch the actuator and brakes while they sit in the truck.

    Next up is to lock out the surge brake actuator.  There are several ways to do this, I'll show what I did.

    Here are the different ways I've seen. 

    1. Swap the coupler to a fixed one. Required cutting the surge actuator off and welding a new coupler on.  I highly recommend this be performed by a professional welder.
    2. Weld the coupler so that it can no longer slide.  This is typically done at the very front / end where the coupler housing ends.
    3. Drill and "bolt" the coupler.

    I decided to drill and pin my coupler using a factory pin.

    Here is how it went:

    First remove the coupler from the housing.  You'll need some snap ring pliers and a hammer.  I believe you can rent snap ring pliers at the auto parts store. I happen to be a tool junkie.

    First make sure the coupler is fully extended, and mark where the then end of the housing is. We'll use this as a measure point later.


    Remove the pins from the coupler:



    Pull the coupler out


    Now we need to figure out the best place for our new pin. 

    On this specific coupler it happened that the shock mount was a great place, and the shock is no longer necessary. 

    Pull the shock out and measure where to drill on the housing.  (This shock and the spring are going to get tossed) (On functioning surge brakes, the spring is used to actuate the master cylinder when the system is compressed)

    Note: On my previous boat there was no existing hole to use, I had to remove the shock and drill through both the housing and coupler to pin it.  That boat had the more standard A-60 surge brake system.





    Now drill.... drill.... drill, and drill some more.

    start with 1/8" drill bit and step your way up.  I ended up with 4 or 5 steps ending just over 3/4" hole in the housing.  



    Now clean up the hole.  we want our work to look good.


    Ok... After looking at the coupler.  The shock provided a spacer for some rollers in the back.  In order to make sure the coupler sits in the housing correctly, the rollers need to go back in. Even though they wont do anything anymore.  Since the shock isn't going back in.... I guess it could have on this one though. I cut the end off the shock to use it as a spacer for the rollers. Also a little bit of primer to scare the rust away.



    Next up:

    put it back together with a new pin.

    Here is where to buy the pin.... It's the only place I've been able to find them.


    UFP Roller Pin Assembly # 34079/A Includes: 2 Retaining Rings #32262 2 Washers #32554 1 Roller Pin #34079 2 Roller Pins Required Per Actuator UFP Part # 34079/A



    Now the coupler won't slide, and it looks like it was made that way.

    Up next, remove the master cylinder from the housing.

    On mine the screws were rusted in place, and I had run out of patience for the day.  So I drilled them out.

    I didn't cover the holes left behind.  Perhaps a future project if it bothers me. (It will :( )

    Note: On the, more standard, UFP A-60 coupler, the master cylinder is part of the structure.  On my previous boat I left it in. If you take it out of this one, then you may need to do some fabricating to restore the structure.




    OK, project is complete!

    Not pictured, I also rewired all of the lights during this process.  That concludes my trailer projects for this year.  Thanks for watching.

    This project took about 6-8 hours.  12 including re-wiring the rest of the trailer.


    Here is my shopping list:

    This kit could simplify your shopping experience:

    If your tow vehicle doesn't already have a brake controller, you will also need one of those.  My truck has one from the factory.

    Tools Required (From memory, may miss some):

    • 1/2" Wrench or socket
    • 7/6" Wrench or socket
    • Drill bits (1/8", 13/64", 17/64", 3/4", 3/16", 1/4", 1/2")
    • Drill
    • 5/16 - 18 Tap
    • 1/4 - 20 Tap
    • Tap Wrench
    • 5/16 nut driver
    • Wire Strippers
    • Wire Crimper
    • Hammer
    • Snap ring pliers
    • 3/8" flare nut wrench
    • 8mm flare nut wrench
    • 11mm flare nut wrench
    • 7/16" flare nut wrench
    • Brake bleeding tool
    • Sharpie
    • Drill punch
    • Tape measure
    • Double flare tool
    • Tube bender
    • Tube cutter
    • Rivet tool and rivets (Not necessary)
    • Hand file.
    • Some paint





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    I have ordered E/H brakes on my new Supra trailer for this year. Another advantage nit listed, is that I can put truck in lower gear and use engine braking on truck to control downhill speed without trailer brakes dragging the whole time. May help with his con of needing to hit brakes more often downhill.

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