If you are renting there is a good chance that the rental agreement will state that you cannot go that far offshore with a boat that size.
That said, as the last poster stated, make sure that you have some sort of communications equipment just in case. Also, when that far offshore it is always a good idea to travel with a friend in a second boat.
Remember, winds can change quickly and kick up some good sized chop or swells quickly. I have my boat (Speedsetr 150) on a bay in eastern Canada and I decided to take a trip across the bay a few weeks ago. The weather was supposed to be nice and calm all day so I took off with a friend in a second boat - the water was dead calm. It took us about 40 minutes to make it across to the other side (about 25 miles). We spent an hour on the other side and then set out to come back. Well, a small head wind started up and between the wind and the growing waves what was a 40 minute trip in the morning turned into a 3.5 hour trip back.
It doesn't take much to slow you down quite a bit in these smaller boats and while the challenger is a bit bigger than my speedster it really isn't big enough in my mind to tackle a 67 mile trip out into the ocean. 134 miles round trip may also be pushing the limits of the boat as far as gas is concerned. If you get slowed up at all because of the water conditions what was a possible 3 - 4 hour ride could turn into something quite a bit longer and gas would become a major concern.