Chris,
Solar chargers are great, but dont buy that one... I purchased one a couple of months ago.. The description says it is weather proof, but it really is not. The directions have you cock the edges to make it weather proof... I did exactly what the directions said, and the solar panel still went bad within 2 weeks: I returned it and went with a 5 amp Coleman solar panel. My Colemen panel has worked great so far; you can purchase them on Ebay for about $80.00 including shipping..
Remember: Stay below 8 amps... If you go with anything bigger, you will have to purchase a charge controller: so you dont over charge your battery. Just another thing to go bad in the boat.
Thanks,
Ken Land
Bullet Lines
www.bulletlines.com