What is your drive ratio? With the speed you are getting @ 5100 you can't be running a 1.5, with a 28 pitch prop. If your drive is a 1.36, and you can spin that 28 up to 5600, you should hit 92 with a 12% slip. With the added boost from having your SC rebuilt, you might be able to pull the extra rpm. How much $$ did Bob charge you for the rebuilt on the 250? Good luck, and hang on.