Trailer Jerks

(chris_b) · (chris_b) **Join Date: Feb 2007** 12-03-2009, 4:04 PM

What would cause my trailer to jerk so dang bad when i take off? This is my second inboard, and did not have the tongue slip this bad on my Moomba. This is a Malibu but both were Boatmate trailers.

(chpthril) · (chpthril) **Join Date: Oct 2007** 12-03-2009, 4:28 PM

Low fluid level and/or air in the lines would be my first thing to check.

(flux) · (flux) **Join Date: Jun 2003** 12-03-2009, 4:52 PM

The shock absorber inside the assembly should be the second.

(nauti4life) · (nauti4life) **Join Date: Sep 2008** 12-03-2009, 4:52 PM

bad master cylinder and or shock.

(rio_sanger) · (rio_sanger) **Join Date: Apr 2007** 12-03-2009, 5:07 PM

HA! I read the post title, I thought it was about the guys that tow in the left lane.

(bill_airjunky) · (bill_airjunky) **Join Date: Apr 2002** 12-03-2009, 5:35 PM

Every trailer I've ever had that had surge brakes did this to some degree after a stop that required some brakes. The jerk is the actuator pulling back out on the master cylinder.

12-03-2009, 5:40 PM

50 bucks says it's a wheel cylinder.

(kraig) · (kraig) **Join Date: Dec 2002** 12-03-2009, 9:36 PM

I bet it's just normal. How much did your Moomba weigh? And how much does your Malibu weigh? This affects how much the actuator pushes in. I never noticed it on my first boat, weighed roughly 3000lbs. My current trailer has the jerk he's talking about with a boat weighing about 4200+lbs.

(newty) · (newty) **Join Date: May 2005** 12-03-2009, 10:18 PM

My money is on low or no brake fluid.
or... bad shock.

(brett564) · (brett564) **Join Date: Jul 2006** 12-04-2009, 2:13 AM

Brake Fluid. That's when I know to fill it back up.

(mattscraft) · (mattscraft) **Join Date: May 2009** 12-04-2009, 6:17 AM

They all will jerk a bit, has to, as the actuator slides out. Angle of the trailer will have a big effect too high or low; make sure you are level, after you check the obvious fluid etc. After stopping, I just ease on the gas a bit to pull the actuator out softly before jumping on the gas.
What is your total weight compared to your vehicle tow rating, if you are very close this will also affect how much jerk you are feeling on takeoff. i.e. 5000lbs rating, 5000lbs total weight. I used to tow a total weight Cobalt with a Jeep Grand Cherokee, 5000lb rating, 5100 lbs boat and trailer, angle was a bit low and you could really feel it jerk. I now have a Ram 1500, 6500 lb rating an 5500lb total weight MC, set up is perfectly level and you still feel a little, but a huge difference.
Only other way around it is to add one of those shock receivers!

(srock) · (srock) **Join Date: Mar 2002** 12-04-2009, 7:06 AM

How well do those shock receivers work?

(superairdawg) · (superairdawg) **Join Date: May 2003** 12-04-2009, 7:18 AM

Sounds like the actuator might have too much travel which can either be air in the lines, or if you have drum brakes they may need adjusted a bit.

A bad dampening shock could be the culprit, as well.

(jumpit13) · (jumpit13) **Join Date: Oct 2006** 12-04-2009, 7:03 PM

if the fluid is low, and you don't have any leaks, check the pads if worn out replace them first and then check the fluid. but just my 2 cents.

(chris_b) · (chris_b) **Join Date: Feb 2007** 12-04-2009, 8:02 PM

well I checked today and the fluid is very low. I will add some and see how it does Sunday when I pull it home for a good winter cleaning. I just got this boat late September so it is still new to me. I am going through replacing things so I know what I have.

(topside_marine)

Chris,

What you describe sounds like a master cylinder that is not functioning as designed for what ever reason. When you look inside the master cylinder is is rusty or very dirty or is it clean and shiny like new metal. Also just adding fluid may not solve the problem. I expect at a minimum adding fluid and then bleeding the excess air from the lines may be your answer but if not you also may be looking at replacing the brake system to fix the problem. Good luck.

(big_b_21v) · (big_b_21v) **Join Date: Oct 2006** 12-05-2009, 1:20 PM

Hey Chris what year is the trailer?
I had the same problem on my 2006 Boatmate Trailer for my Supra. I could never get it fixed but heard through one of the service guys that they had a run of trailers with a bad cylinder or too short of cylinder, something like that.
I could never get anyone to warranty it. It was never a problem other than being annoying, but I would imagine that over time that jerk when you take off cant be good for the welds on the trailer.