I'm new to boating and we just got a small fiberglass boat. About 15 ft. I think, and no markings,so I have no idea what kind it is - although it's a safe bet that it was built before 1970.
Here's the boat: http://www.flickr.com/photos/35181850@N04/3260439431/
So, question is: how do I know what type of motor to put on it??
First things first, it sunds like you don't even have a title to the boat. You should look into the laws of your state as far as boat titles and registration, without a title you may be up the proverbial creek. First question to ask whenever buying a boat "DO YOU HAVE CLEAR TITLE"? Should you be able to register the boat then keep in mind that the cost to power the boat should include controls and gauges. Good luck.
My Dad had a boat similar to this one years ago. It first had a 25hp Mercury outboard. Later as me & my brothers got older (and heavier) we learned to water ski. A Mercury 40 hp was next, then a Merc 50hp with a power prop. It ran great & would pull two big young men ( we weighed maybe 175 each). I believe that we had to use two skis each to start off. Once skiing we could kick off a ski and slalom. I think the boat was not terribly overpowered and it would really scoot. We had a great time with that boat all the way thru college.