Trailer tyre wear

If you put too much pressure in the tyre, you are transferring all the road bumps straight into the boat, as the suspension on most trailers is rated far too high for a lightweight dinghy. 25 psi sounds about right. I do wonder too whether it is wearing on the mudguards when the suspension is bounced, or something along those lines. I find trailer tyres crack on the sidewalls before they wear out, even doing high miles. And that takes years.

I would suspect rubbing on the mudguard but do consider the tyre pressures.  A boat is really quite light and so the tyre pressures would need to be low.  I trail a 4000 - some would say a heavy boat - but nothing like a Wayfarer and so with 10inch mini wheels I find about 15psi about right.  You should see some deflection of the tyre wall when its at rest but the best test is to test their temperature after a run.  By hand you can tell if they are hotter than your car tyres if so put an extra couple of pounds in, if cooler take a couple of pounds out.

In all my experience of trailing my tyres have never worn out but have had to be replaced because of cracking of the side wall due to UV degradation.  I expect dozens of thousand miles from a tyre.  However as a second thought slack bearing would allow the tyre to woble and that would increase the tyre wear considerably I would have thought.

600 miles, at that rate i'd be changing tyres every two open meetings... ummm silly question but are you absolutely sure they are actually bald after that distance??? I'm pretty sure i've covered well over 6k in the last year and a half and mine are nowhere near illegall.  Have you been competing in some sort of trailer drifting competition by any chance????