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Demco Hydraulic Drum Brake Assembly - Single Servo - Galvanized - 10" - Right Hand - 3,500 lbs

Demco Hydraulic Drum Brake Assembly - Single Servo - Galvanized - 10" - Right Hand - 3,500 lbs

Item # 18787
Our Price: $65.79
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Demco Accessories and Parts - 18787
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Passenger's-side hydraulic trailer brake assembly features a single-plunger design. Galvanized steel resists rust, making the assembly great for boat trailers. Mounting flange has 4-bolt pattern. 1-800-940-8924 to order Demco accessories and parts part number 18787 or order online at Free expert support on all Demco products. Great prices and Fastest Shipping for Demco Hydraulic Drum Brake Assembly - Single Servo - Galvanized - 10" - Right Hand - 3,500 lbs. Accessories and Parts reviews from real customers.
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  • Reviews (44)
  • Q & A (0)
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  • Why etrailer?

Demco Accessories and Parts - 18787

  • Trailer Brakes
  • Hydraulic Drum Brakes
  • Brake Assembly
  • 10 x 2-1/4 Inch Drum
  • Demco
  • RH
  • Single Servo
  • 3500 lbs

Passenger's-side hydraulic trailer brake assembly features a single-plunger design. Galvanized steel resists rust, making the assembly great for boat trailers. Mounting flange has 4-bolt pattern.


  • Marine-grade hydraulic drum brake assembly is great for boat trailers
    • Designed for use with surge-type trailer brake actuators
  • Sturdy, corrosion-resistant steel construction
    • Galvanized backing plate
    • Stainless steel spring hardware
    • Zinc-plated wheel cylinder
  • Single-plunger design delivers 15 - 20 percent braking in reverse
  • Riveted brake shoes provide increased durability
  • Periodic manual adjustment required
  • Mounting bolts sold separately
  • Made in the USA


  • Configuration: right hand (passenger's side)
  • Dimensions: 10" diameter x 2-1/4" thick
  • Mounting flange bolt pattern: 4 on 4"
  • Wheel size: 13" - 15"
  • Axle rating: up to 3,500 lbs
  • 1-Year warranty

SB18787M Demco Galvanized 10" Marine Trailer Brake Assembly - Single Servo - Right Hand

California residents: click here

Customer Reviews

Demco Hydraulic Drum Brake Assembly - Single Servo - Galvanized - 10" - Right Hand - 3,500 lbs - 18787

Average Customer Rating:  4.9 out of 5 stars   (44 Customer Reviews)

Passenger's-side hydraulic trailer brake assembly features a single-plunger design. Galvanized steel resists rust, making the assembly great for boat trailers. Mounting flange has 4-bolt pattern.


I’ve purchased items from etrailer over the years and they have never failed me getting the correct parts and on time. Thank you!


Wheel came off boat trailer, must have bent backing plate. New huds rubbed and would not turn. Got new plates from etrailer fit perfect. Got here fast and easy to install.


Put new brakes,drums, bearings and seals and hubs on boat trailer found all parts here and received really fast always order parts for trailers here and always will


Quick and easy assembly with all the information needed


When I realized my brakes were in need of repair and no local shop worked on trailer brakes I decided to do it myself.
With the help of the etrailer folks I had a new set of brakes and was ready for another fishing season.
Great products, they do what they say and great customer support.


Good product should coat all with non corosive coating and provide pre drilled wash out ports. Cad or Zinc plated bolts would be good as have to track down at an auto parts store and wern t plated.


These worked great. Much easier to replace the whole assembly like this, than replacing all of the original rusted out components. These are galvanized, so they should last a long time. I'm using these for a boat trailer for a 21 foot fiberglass euro styled V8 powered pleasure boat that weighs about 3000 pounds.


So happy i found etrailer. They had the quality parts i had been looking for at a great price. I am equally happy with the speedy free shipping. I recieved the brake assemblies and installed them in less time than it took to locate them. Thank you. You will be my go to trailer parts supplier for all future parts. I have 5 different trailers and am sure i will require your services.
Robert K.


After going to numerous trailer stores and auto part stores in my home town I called Bill at etrailer. I found Bill to be very professional and helpful.. The package was ordered on Monday afternoon and was on my door step on Wednesday afternoon. The item was exactly what I had ordered. I will continue to purchase my trailer needs from Bill.


Good price and bolted up perfect! has great prices and fast shipping when you need your parts fast. This is the 3rd complete trailer rebuild and I wouldn't think about buying from any other supplier.

Bobby M. Maryland


The product was first quality. It was packaged very well. Easy to install and yes, I wished I had ordered new bolts and nuts. Mine were a little bit rusty being on a boat. The only differences I noticed were that my old wheel cylinder was made of aluminum and this one was made of steel. Steel will rust but it will probably last longer.


Nice quality product. Easy to install... Well, as easy as any brake job could be. Spend a little bit and buy new bolts when you do this job.


Parts arrived exactly as described and worked perfectly. Great price, shipping was fast considering how far it had to come and arrived when it said it would. I've already ordered more parts from here and will continue to in the future.


I have great service with Etrailer. Ordered the wrong part,called and was completely taken care of. Easy to do business with.


Great products. Expert helpful videos for adjustment and installation. OEM parts and cross referencing made easy. Will buy products again on next axle rebuild.


Great products at great prices!


Great products with great prices.


Very simple to install. Unbolted old and installed new and adjusted. So easy even a caveman could do it.


As advertised, no problem to swap the old with the new.


Easy to install and fast shipping



Perfect fit. Just with it came with nuts and bolts.


Everything as expected.



Review from a similar Demco Galv Single Servo 10 Inch in Accessories and Parts

Put new brakes, drums, bearings and seals and hubs on boat trailer found all parts here and received really fast always order parts for trailers here and always will

Show More Reviews

See what our Experts say about this Demco Accessories and Parts

  • Troubleshooting Surge Trailer Brakes that Make Hammering Sound When Applied
    I bet it's a worn out suspension component that's flexing as the trailer pushes into the surge brake actuator and once the brake applies it pulls itself back and repeats the process quickly causing the hammering sound you are experiencing. Check out the suspension of the trailer to see if you can find any worn components that would cause this and fix as needed.
    view full answer...
  • Surge Brake Actuator Recommendation for Use with Assemblies 18788/18787
    The brake assemblies # 18788 and # 18787 are not free-backing. For picking out an actuator the part # 8605001 would work well as it has more capacity than you'd need, is for drum brakes, and is for a 2 inch hitch ball.
    view full answer...
  • Solution to Allow Trailer with Surge Brakes to Back Up
    You can install free-backing brake assemblies that won't activate when the trailer is backed up or you can install a lockout on the actuator. I attached a link to a page that has all of the free-backing assemblies we carry for you to check out. You'd need to measure the dimensions you currently have and then match the size you need by selecting it from the filters on the page. I'd need to know what brand of surge actuator you have to pick out the correct lock out you'd need.
    view full answer...
  • How to Find Surge Coupler, Wheel Cylinders and Bearings for 1997 Eagle Double Axle Boat Trailer
    For the actuator, you'd want to choose one compatible with drum brakes with sufficient capacity for the weight of your trailer. You'd also need to choose between a bolt-on or a weld-on application, the trailer ball size and the lock-out desired (none, manual or electric). You can see our selection by clicking the provided link. The wheel cylinder is a likely place to check for leaks, but if the trailer's been sitting for awhile, you might be better off replacing the brake assemblies,...
    view full answer...
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  • Removing Surge Coupler-Actuated Brakes from Mc Clain Boat Trailer
    If you want to deactivate the hydraulic brakes on your boat trailer, you can certainly do so. The simplest way to do this would be to drain the brake fluid from the lines by disconnecting the brake lines from the wheel cylinders and allowing the fluid to drain. You'd then immobilize the articulating portion of the coupler by drilling holes in either side and sliding a bolt through to prevent the coupler from compressing. A better long term option would be to remove the coupler and replace...
    view full answer...
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  • Electric Reverse Lockout On Boat Trailer Surge Coupler is Not Working
    On a trailer that has a surge coupler, if the trailer does not have a manual or electric reverse lockout or free-backing brakes then the brakes will engage when backing up. Free-backing brakes are only available in drum brake applications. So you would have to have a coupler that has either a manual or electric reverse lockout feature. It sounds like you have an electric lockout. An electric lockout will be at the back of the master cylinder. It will be grounded to the trailer frame...
    view full answer...
  • Disc Trailer Brakes are Weak on One Side After Replacing Calipers and Pads and Bleeding Brakes
    Like you said, you don't want the trailer wheels to lock up all the time. They should stop the wheels proportionally to how much force is exerted on the actuator. With that said it could be that you are not physically pushing in the actuator all the way to reach lock up. There could also be a leak somewhere but I think you would notice fluid dripping out. Sometimes the brake lines are not large enough depending on how far the actuator is from the calipers. A larger diameter brake line...
    view full answer...
  • How to Determine if Trailer Brakes are Require for a Boat Trailer
    That is going to depend on a few things. You will need to check with your local DOT to see what the requirements are for trailer brakes. You will need to know the weight of your trailer as well. Depending on the weight of your trailer will also affect how many brake axles are required. I attached a couple help articles on adding brakes to a trailer for you to check out as well.
    view full answer...
  • How to Know When a Trailer Coupler Shock is Bad
    If your trailer wants to slam forward and back as you apply the brakes of your tow vehicle the shock is bad and needs to be replaced. When a shock goes bad it no longer dampens the movement of the actuator which causes what I described. If the shock you have can easily be extended and retracted then it needs to be replaced. I attached a page that has all of the replacement shocks we offer.
    view full answer...
  • Trailer Surge Coupler Can be Pushed in By Hand and Brakes are Weak
    The coupler should be very difficult to push in by hand but it doesn't return on its own. There is likely a problem inside your coupler that will need to be addressed to get it working properly again. It is most likely the shock that is inside. There are replacement shocks but I would need to know the manufacturer and model of the coupler you have. I have included a link to the shocks we carry. If you can't find a part number or manufacturer on the coupler then you may be able to find...
    view full answer...
  • Will Surge Actuator Master Cylinder Fill Up with Fluid When Pistons are Compressed
    When you force the pistons down in the caliper to install new pads you will end up forcing the fluid back from the calipers into the master cylinder since it has no where else to go. So it will fill the master cylinder up. The system is designed for massive amounts of pressure so I really doubt you blew any seals by compressing the pistons like you did. I would try taking the trailer around the block to make sure it's not leaking though just to be sure.
    view full answer...
  • Troubleshooting Reverse Light Fuse Blowing and Reverse Lockout Solenoid Wiring getting Hot
    It sounds like the problem is in the wiring of your reverse lockout solenoid. Most likely the circuit is shorting out somewhere and is causing the circuit to over-draw which is why the fuse is popping and the wire is getting hot. I would inspect the wiring of the circuit and see if you can find any obvious signs of a short and fix as necessary. Cut or exposed wiring or corrosion can cause shorts. I attached an FAQ on trailer wiring for you to check out also.
    view full answer...
  • Troubleshooting Weak New Hydraulic Drum Trailer Brake Assemblies
    Keep tightening them until you feel a light drag as you turn the wheel. That should give you the proper tightness to lock up the wheels. Sounds like they are still too loose. Also you should try towing to see how it performs then.
    view full answer...
  • Troubleshooting Surge Brake Actuator that Won't Release Brakes
    Sounds like your trailer has an electric reverse lockout which prevents the brakes of your trailer from applying so that you can back the trailer up. If now the brakes won't release after the issue you had with someone else backing up the trailer that sounds like a mechanical problem. Possible something has bent inside the surge actuator which won't allow the inner piece to slide forward and release the brake pressure. You should inspect the coupler looking for any damaged or bent components...
    view full answer...
  • Troubleshooting Trailer Brakes Locking Up When Driving Forward
    Unless the trailer became completely unattached from your tow vehicle causing the breakaway pin to be pulled out, forgetting to lock the coupler to the hitch ball, while certainly something you want to double check the next time you tow, would not have caused the trailer brakes to engage during travel. The brakes locking up when going forward was likely caused by some kind of short in the trailer wiring. I recommend inspecting the brake output wire on the trailer for any exposed portions...
    view full answer...
  • Will Hydraulic Disc Brakes Still Activate if Power to Trailer is Lost
    With surge type hydraulic brakes on a trailer they will still stop the trailer regardless if the trailer wiring loses it's connection. That's actually an advantage to this style of braking. If you have electric over hydraulic brakes that have an actuator that is controlled by an electric signal from a brake controller you would then lose brake power if the trailer lost it's connection. Typically it's corrosion on the trailer connectors that causes the connection to be lost. Cleaning the...
    view full answer...
  • Troubleshooting Locked Up Brakes After Using Bearing Buddy to Put Grease in Hub
    Sounds like you made the easy mistake of putting too much grease in your hubs with your Bearing Buddies and it blew out your seal and emptied the grease out and damaged the bearings and that's why the wheels are locked up. So you'll need to pull the hubs off and inspect the bearings and spindle and replace as needed. If you get me the bearing numbers or axle capacity I can help you find that info.
    view full answer...
  • Boat Trailer Brake Assembly Recommendation for a 3500 UFP Axles
    Yes, the Demco Hydraulic Drum Brake Assembly # 18787 would be the correct assembly for the right hand side of your trailer and the part # 18788 would be the correct assembly for the left hand side of the trailer. If your current brake assemblies only have a 1-3/4 inch width they are not fully utilizing the 2-1/2 inches of drum width that you measured. The bolt pattern of the flange is also the same as what you have. Check out the picture I attached to see these measurements. These assemblies...
    view full answer...
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  • Correct Replacement for Atwood 159-80770 Braking Assemblies
    Yes, the Demco Hydraulic Drum Brake Assembly part # 18788 for left and part # 18787 for right will work well to replace the Atwood 159-80770 Braking Assemblies. They are both 10" x 2-1/4" with a 5 bolt flange so there will be no compatibility issues.
    view full answer...
  • Determining if Replacement Shock is Needed for Brake Actuator
    A shock like the Replacement Shock # T1242600 for Titan Model 6 and 10 Brake Actuators is essentially designed to dampen the movement of the actuator. There are a couple things you can do to see if a replacement is in order. First, if you find that your trailer is slamming forward and back as you apply the brakes in your tow vehicle, this is an indication that the shock has gone bad. Also see if the shock can easily be extended and retracted without any resistance. This would also indicate...
    view full answer...
  • Troubleshooting 2012 Glastron Boat Trailer With Catching/Slipping Brakes When Moving After Stop
    With your boat trailer, you will have a brake actuating surge coupler. This means that when you brake the hitch ball will pressurize the plunger of your master cylinder applying hydraulic pressure to your brakes. Once stopped the internal shock like # T1242600 should release that pressure and it should allow pulling again without a catch. Since you are feeling a slip or catch, it is likely that shock is not returning correctly to the pulling position. This is likely the issue if there...
    view full answer...
  • Recommended Surge Brake Solenoid for Backing Up Boat Trailer
    If you have the single servo brakes like the Demco Hydraulic Drum Brake Assembly - Single Servo - Galvanized - 10" - Right Hand - 3,500 lbs # 18787, then you should have the free backing. However if you have an odd angle that can impact the backing up so I do recommend adding the solenoid with the electric connection to your vehicle's reverse light circuit to keep your brakes from engaging. I recommend using the Replacement Solenoid Valve for Titan Brake Actuators with Reverse Lockouts...
    view full answer...
  • Why Aren't Hydraulic Brakes Locking Up When Backing Trailer Up Hill When Unplugged from Vehicle
    It could potentially be a bad solenoid on your actuator that was closed shut that's preventing the brakes from engaging in reverse on your trailer, but there are a few other possibilities that you can check as well. I'm not sure if you're backing up with the trailer unloaded (or if it's just a really light trailer) but if it's not heavy enough and the hill isn't steep enough, it simply might not be creating enough pressure to activate the brakes. If it's unloaded you can try loading up...
    view full answer...
  • How To Check if Trailer Surge Brakes Are Working Properly On Tandem Axle Boat Trailer
    Checking the brakes can be done in two ways. The easiest way is to raise one side of the trailer and spin the wheels while someone applies the surge brakes at the coupler. The better way would be to remove each of the wheels and brake drums and activate the brakes while making sure the wheel cylinders and brake assemblies are functioning properly. After this the first thing I would do is bleed the brakes using the trailers surge coupler to force the fluid from the brake lines and make...
    view full answer...

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