Looking For New Leaf Springs Or Over-Under Kit For Single Axle Boat Trailer

Updated 06/08/2026 | Published 04/19/2026

Question:

I have a 1995 Mastercraft Prostar 205 boat. The boat is on a single axle manufacturer original trailer. I am having problems with tire sidewall scrub in the wheel wells when hitting bumps. I’m not sure if this is an original problem or if the springs have sagged under load. I removed and measured the springs and they match up to original specs. Do you have a kit where I can add a leaf spring, replace with heavier springs, or do an axle over spring conversion? What do you recommend? I think the spring capacity of 3500 pounds is at the limit with the trailer and boat weight. Please let me know what products you may have that can help me with this issue. Thank you, Paul LaBelle

asked by: Paul L

Expert Reply:

Hey Paul, thanks for reaching out. It could be the old leaf springs are worn out and are flexing more than they should under a load. New springs should help with this, and we can even look at doing a slightly higher rated spring to help support that load better. We don't want to overkill the capacity too much though. Depending what length the springs are we may have a slightly heavier spring option.

We do have over-under kits too, I'd just need to confirm your axle diameter to make sure you get the right thing.

For example, the Dexter Trailer Springs Over-Under Conversion Kit # K71-384-00 is for a 2-3/8" axle.

Let me know your spring length and axle capacity and I'm happy to look into it and see if we have a good spring option for you.

expert reply by: Jesse M

Rod

4/24/2026

I switched to an over/under kit for a Dexter axle on a 2012 Jayco single axle camper last Spring. It added 4” more clearance in my wheel wells, and was fairly simple for two mechanically-minded guys to install in a few hours. It was the BEST thing I could have done to improve that little unit. Well worth the money I spent on it.??

Jesse M.

4/24/2026

@Rod Nice! Sounds like the over-under kit was exactly what you needed. Glad to hear it worked out. Thanks for sharing!

David G.

4/24/2026

I have used the over/under kit for two different trailers that I have, an old 5th wheel RV frame that I converted to a flatbed and a conventional flatbed trailer. The kit goes on easily and makes a solid platform. I did have to take out the kit on the conventional flatbed because it lifted it up to high to load up my Durango. Make sure you really need the lift, add up the height of the springs and the axle diameter to see how much the actual lift will be.

Jesse M.

4/24/2026

@DavidG Hey David. Yea you are exactly right the over-under kits lift the trailer the diameter of the axle plus the thickness of the spring pack. So, it's not always the exact same about of lift depending on the spring thickness. Thanks for sharing that tip!

Paul L.

6/4/2026

Hi Jesse, Sorry for the late reply. I have what appear to be 28” length double eye leaf springs. There is a welded mount on the trailer frame in the front and a drop shackle in the rear. The springs are 1-3/4” wide and 1/4” thick. The axle tube is square. I have no idea what the axle weight rating is. The boat weighs 2550 lbs and id imagine the trailer is close to 1000 lbs. I’d like to bump up the spring capacity to 4000 lbs.

Jesse M.

6/8/2026

@PaulL I gotcha. Unfortunately, we don't offer any 28" long springs. The closest we have is a 27" long double-eye spring for a 3,500 lb axle part # e36FV. This might be a bit too short to fit into your suspension though. Usually the acceptable tolerance is +/- 1/2" so you'd be cutting it close with those. Also, we do have U-bolt kits for square axles, it just depends on the size of axle. For example, the CE Smith U-Bolt Kit # CE23103 is for a 2" square axle. When you measured your leaf springs, did you raise up one side of the trailer? Or was it on the ground?