Yup, marine radios have more power than CB's, and illegal to use them for other than marine use.
25 miles through wooded forest is going to tax any radio, especially if your not on top of the hill, or don't have repeaters to use. I've talked 15 miles on simplex 2 meter in hilly,wooded terrain and it worked but I wouldn't totally depend on it. Handheld radios do lack the punch through power, than say a 75 watt mobile/base rig. Think big tall antenna. I have my larger antenna on my p1k mounted in the bed (not connected to radio), until I need it. Then I remove it from its mounting, and attach it to the coax on my homebuilt plate when I want to use it. If the trail is tall enough I run with it attached, and I have a spring so it will bend, but I don't like a smashing the antenna against treatment branches. Don't want to nick the outer coating that protects the fine wire that is wrapped around the antenna mast. Good news if you use 2 meter radio is that the antennas are fairly short, unlike a cb.