Sorry guys, i'm a former diesel mechanic so when i heard cat i automatically see big yellow engines. If you look at the chart there its just measuring from the opening of the pass, when i left for my trip there was a decent trip to just get to the pass, which would add some miles.
I do agree Chris_b that the cost are something that is keeping more people away, and i have actually been rolling some different ways to help out the local divers.
Kalik has another point, now this would kind of go against what Chris_b was looking for but if you were the first to book would you be against a small charge that would guarantee that the boat will go to the dive sites you want to, and if anyone else books they have to either go to your spots or wait for another trip? Typing it makes it sound like a worse idea than it did in my head.
Something that might address both of your problems would be what i would call having a "Crew", or a group of people that you go diving with often. When your crew books the boat, i would say 3 or more people, the boat goes where you want to go that day, and ever time your crew books the boat you would get more of a discount until you reach a certain level, lets say Chis_b's 75%. This way you would have more commraderer and maybe there could be some kind of competition we can work out between crews for a free trip. BTW if i can i would like to make the boat a spearfishing boat also.