What Surge Brake Actuator do I Need to Replace Mine on 21' Boat Trailer with Fold Away Tongue?
Updated 03/02/2026 | Published 02/27/2026
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Question:
Hello, I have a boat trailer in need of a new surge brake actuator. The unit has a swing tongue and I have already removed the entire actuator if I’m picking a new actuator for instance, one that has the weld done would I just remove it from the primed piece and slide it into my existing part? 21 for boat , single axle trailer with disc brakes, and electric lockout
asked by: Vince R
Expert Reply:
Hello Vince,
It sounds like are running into a similar situation as I did with my 2004 Ranger trailer about 3 weeks. I got home from a day of fishing at Lake of the Ozarks and went out to the garage the next day to find a whole lot of brake fluid on the ground. Not a great surprise.
Yes, you can just order the inner member of the surge brake actuator and slide it right into your fold-away tongue. I attached a picture of mine so you can see exactly what I’m talking about.
Most likely you’re replacing an older UFP surge brake actuator. I attached a photo of the sticker from mine so you can compare. If that’s what you have, you’ll also have a bypass solenoid. Mine was mounted behind the fold-away tongue and had two brake lines running into it. The newer solenoids are mounted directly on the back of the actuator, so the wiring setup is a little different.
Here’s what you’ll want to order:
Replacement Inner Member for Dexter DX7.5L Actuator - Single Axle w/ Disc - 2" Ball - 7,500 lbs # DX39FR, this will give you a new inner member and solenoid for you single axle set-up.
If you do have the bypass solenoid, you will need to replace the flexible brake line while you’re in there, as mine did not have the right fittings for the new set-up. You will need one of the following, mine was the 25": 25" Dexter Hydraulic Brake Line with Fittings - 25" Long # T0980100, or for 18-25/32" Long # T0776500
You will also need some shrink wrap butt connectors like the Deka Heat Shrink Butt Connector # DW05744-5, and make sure you have a set of snap ring pliers to make things way easier!
When you’re ready to bleed the brakes, start with the caliper that’s furthest from the actuator, following the brake lines. On the old UFP unit it was honestly a pain to bleed, but this one is much easier since you can use a screwdriver to manually stroke the actuator.
You’ll need a second person to help. One person should watch the bleeder screw until you’re getting solid fluid with no air, and the other person should stay at the actuator. Make sure the DOT 3 brake fluid (can get from local auto store) never runs dry in the reservoir, and use the screwdriver to slowly push the actuator in to move fluid through the system. If it runs dry, you have to start over.
What kind of boat do you have sitting on that trailer? Where are you fishing and what are you catching? I use to mainly stick to crappie, but now I chase the Bass! I fish some small local tournaments at Mark Twain Lake and Lake of the Ozarks here in Missouri. I am still on the chase for that double digit Bass =)
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Product Page this Question was Asked From
Replacement Inner Member for Dexter DX7.5L Actuator - Single Axle w/ Disc - 2" Ball - 7,500 lbs
- Accessories and Parts
- Brake Actuator
- Disc Brakes
- Inner Member
- Dexter
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