More than anything else...
Get a good antenna with as much height as you can go with... not so much the length of the antenna, but mounting. VHF is all about line of sight, so the higher your antenna, the further you go. Even with a HUGE amount of power, you still only get a straight line of propagation.
There are lots of good Marine Radios out there... good means EXPENSIVE. Realistic makes a good one, but go for a premium brand if you want it to last a long time. ICOM is best, a lot of the cruising yachts use them in Hawaii, Uniden isn't too bad either....