How to replace boat trailer leaf springs

I keep my 19ft trailer-sailer fully rigged around 100m or so from a public boat ramp.

Towing distance has never been a major concern.

However, following a recent launch I realised that my trailer suspension was horribly corroded.

An angle grinder with a cut-off disc makes short work of rusted hardware, such as U-bolts. Credit: Steve Walburn

Replacing the leaf springs had been on my mind for some time, but now my boat was tied up at the marina with a storm on the way and no way to recover her.

A little online research had the necessary parts on order that same day, and by the following evening I’d replaced both leaf springs and was able to retrieve my boat before the blow rolled in.

Use a small bottle jack to support the trailer frame when removing and installing components. Credit: Steve Walburn

When it’s time to show your trailer some love, here’s what you need to know about replacing a leaf-spring suspension.

First, this simple DIY job is much easier with the right tools.

The most important weapon is an angle grinder with a cut-off disc for removing old U-bolts.

An impact driver and a shot of penetrating lubricant will help free nuts and bolts that have seized from corrosion. Credit: Steve Walburn

Keep an extra blade on hand because the working space is tight, making it easy to snap a disc.

An impact driver and a small bottle jack are also handy.

The impact driver makes short work of seized nuts and bolts, and the hydraulic jack enables you to raise and lower the trailer
to manoeuvre components into place.

With the old springs removed and the trailer supported, fit the new leaf springs loosely in place. Credit: Steve Walburn

The second thing to remember is that there are several different styles of leaf springs.

Some have an eye on each end, others have one eye and a flat ‘slipper’ on the other.

Measure your existing springs and hangers carefully before ordering.

With new springs and U-bolts in hand, park your trailer in a level spot that is easy to clean.

I made the mistake of doing the job on a lawn and had to spend an hour with a magnet bar clearing a minefield of rusted metal shards.

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Spray penetrating lubricant on any nuts and bolts that need disassembling.

While the lubricant is soaking in, support the trailer frame with the bottle jack to take pressure off the suspension.

Then cut off the U-bolts. Remove the bolt (or bolts) that connect the leaf spring eyes to the trailer frame and disconnect the old leaf springs.

Tighten fasteners in rotating order, making your final round with all the weight back on the suspension. Credit: Steve Walburn

Slide the new leaf springs underneath the axle and get one end lined up with the bolt flange on the trailer.

If the spring has only one bolt eye and a flat slipper on the opposite end, like mine, seat the slipper end first then line up the bolt hole.

Loosely position the new U-bolts around the axle and springs.

Raise or lower the bottle jack as necessary to align the remaining eye bolt with its corresponding flange.

All finished. Replacing leaf springs is a fairly straightforward task. Credit: Steve Walburn

Alternately tighten all fasteners until you have everything seated.

Lower the bottle jack all the way and tighten everything one more time for good measure.

The job takes about a half day and is easier on the wallet than towing your trailer to a repair shop – that’s if it’ll even make the trip!

Enjoy reading How to replace boat trailer leaf springs?

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