Here is a link to a Performance Test from the Alumacraft web site with your exact boat and motor. They got 52 mph with a 14.75x19" BRP Viper mounted in the second hole at 5400 RPM. Now there was a 15 mph wind during the test, so I don't know if they achieved top end with the full 15 mph at their backs, but 52 is pretty good.
http://alumacraft.com/images/stories...75-Etec150.pdf