I would definitely have a spare on that! What are you going to do when you get a blow out (which is what is likely to happen)? You or your boat will be stranded.
Also, may be time to at least carry a spare winch strap. Depending on how many miles you tow I'd be thinking about re-packing those bearings rather than just lubing them. Brakes on this trailer?
_________________
Former owner of:
1996 Four Winns Horizon 200 5.8L VP
2006 Four Winns Horizon 260 8.1L VP
2007 Sea Ray 290 Sundancer
Current boat
2004 Sea Ray 290 Sun Sport Twin 350 Mags