Boating for Dummies 101: Part 1 – Trailer Axle Alignment

by | Mar 23, 2016 | Articles, Trailers and Towing

an article by Dom Appay (Feb 2016)

Last year when I bought a 2nd hand 5m fiberglass boat on a 09 Dunbier Trailer which was pretty greasy in a lot of places, making it look tired but okay. Not being familiar with boats and trailers, I had a lot to learn. Over the next 5 trips, I got familiar with towing a trailer boat. I found both tyres were wearing unevenly on the LH edge, the mechanical brakes were sticky, and it moved around more than I expected when towing.

Tyre Wear: was caused by the axle “Crabbing”, ie. being out of alignment with the trailer frame.

Tyre wear

Axle Measurement:

I realigned the axle by measuring the LH and RH distances from hub to coupling, and moving the axle subframe. The RH axle was trailing the LH axle by 25mm.

Axle Measurement

How to Align your boat Axle:
  • Tie a string line around the RH hub and mark the string at a point on the middle of the coupling
  • Do the same on the LH hub and mark the string at the same point on the coupling again.
  • Measure the difference between marks.
  • This is the distance the axle has to be moved.
  • I marked the distance on the LH frame, loosened the 2 axle U bolts and knocked the axle backwards until the mark lined up.
  • I remeasured with the string line and stopped moving the axle when both string measurements were equal.
Next month: Replacing your trailer coupling