How To Replace An Old Square Boat Trailer Axle

Question:

I need to replace a boat trailer axle. The axle tubing is square so would i need to replace the ubolts and all? also it looks like my spring hangers are at 75 inch centers not 74 and the springs set on top of the axle and not underslug. What do you suggest? Also I know it had brakes on it but i do not need them I need an idler axle instead of a brake axle.

asked by: Tracy D

Boat Axle
(click to enlarge)

Expert Reply:

Hey Tracy,

In order to get the right axle we'll need to know the axle capacity, hub face to hub face measurement, and spring center measurement. I'm assuming the trailer is pretty light and you most likely have a 3,500lb axle. We can try to verify that with any part numbers you can get off the bearings, grease seal, or hubs. You can measure for the bearings and grease seal using a caliper # PTW80157 and the diagram below. For the hub face measurement you and a helper can run a tape measure across and it sounds like you already measured 75" for the spring centers.

You would need to replace the u-bolts since you're switching to a round axle, and because you typically would have to cut off the u-bolts since the nuts tend to seize up from rust over the years.

expert reply by: Kevin C