VHF range is not an issue for contacting the Coast Guard. Their Rescue 21 coverage system is designed to communicate with a handheld radio at a height of 6 ft operating at low power (1 watt) over a range of at least 20 nautical miles offshore. The Delaware/NJ area is very well covered by several different sectors.
The most important factor for VHF communication with other boats is antenna elevation rather than power or antenna gain. At 25 W, a 3 db gain antenna has plenty of power to reach anything on the horizon. That's why sailboats only use 3 db antennas on their masts. While it's true that an 8' - 6 db antenna mounted on a hardtop will have about a 40% greater range than a 3 - 3 db antenna when talking to another boat with the same setup, there is a downside. In an active area, you will have 40% more radio chatter interfering with your calls.