Any recommendations for a small trailerable outboard powered boat that can be used safely offshore?
I was thinking a 5m rib but was put off because can only afford used and am worried about uv degradation of the tubes.

5 metre rib for offshore use would be rough as ****ing guts , no cover from spray and generally uncomfortable .

I have a 6.5m gemini RIB for going out to rottnest and while a very safe boat , once it gets rough it's not the nicest ride .

You'd be better off going to a fishing site for this as they live and breathe for their boats. Fishwrecked is probably the best one if you are not a keen fisho as the crowd there is the most pc of the fishing sites.

What's the plan for offshore? Anything over 4m is fine given the right weather but if you want to get out deep regularly you're going to need a substantial boat, big 4wd to tow it etc.

BOAT - Bring On Another Thousand.