Hope this is not too far off topic...

The leaf springs on my boat trailer squeek something terrible. They are monoleaf springs on a rectangular tube axle. I have tried spraying some WD-40 into the bushings and around mounting plates and that quiets them for about a day, then the squeeks are back. Any ideas on what I can use to lube them up that will last?

Thanks

Pat

P.S. Since the trailer has aluminum wheels and carries a 70 mph boat, maybe it qualifies as Hot Rod related after all...