What should I use to prevent scratches and scrapes on the bottom of my pelican bass boat ? Its plastic and has seen some use. I don't want it to leak and want to put something on it to keep it from leaking. What should I use ?

Are you looking to just fill them in? 3M 5200 should work fine. It's bright white in color if it matters.

Scratches & scrapes are battle scars, if you want to avoid them, just don't drive your boat where you are likely to get them.  If your boat is currently leaking, that is a different story.  It occurs to me that 6 months or so ago I read a thread about welding ABS plastic.  I couldn't tell  you if it was on this forum or on the tin boats forum.  From what I recall, it seemed like a pain.  Surface preparation was critical and you actually spent more time preparing the surface than you did welding it.

Search welding plastic and see what you come up with and if nothing comes up here, go over to the tin boats site.

http://www.madrivercanoe.com/education_portal/index/learn/repairing_polyethylene_cracks_and_fractures