Re: What make is this old boat?
I think Eric is right about the boat being a Feather Craft. I just found the following website, which I think confirms his opinion. The boat appears to be a model called a Ranger III, which seems to have been made starting in 1956. If you go to the second link that I have provided, you'll see the brochure page for the 1957 model, which is a pretty good bet as being what you have.
Feather Craft also made a boat called the Vagabond, which is very similar in appearance but is 6" longer. I don't think that is your boat, however, because the barrelback shape is somewhat different and the transom doesn't have the "drop down" shoulder that the Ranger does.
The third link is for the serial number page of the website. It says that the Ranger series boats had serial number that began with RIV. That was followed by month of production, production number, year that the boat was built, model year, and color of anodizing.
http://www.feathercraft.net/
http://www.feathercraft.net/image-viewer.htm?catalogs/1957/57ranger14seriesfc.jpg
http://www.feathercraft.net/FCSerial.htm
PS: Here's a forum that might help too.
http://www.activeboard.com/forum.spark?forumID=729&subForumID=336081&p=2
PS #2: I just noticed that there is an owners group for Feather Craft right here at iboats and that it contains a link to the site I provided, above. There is only one post there, but it looks like we have two members that own one of these boats. They might be helpful in advising you.