Generally, switching from 3 bladed to 4 blade props will help with your "hole shot", with slow speed handling may inprove top end speeds a little bit. The reason is because the 4 blade props have less pitch per blade than a 3 blade props and that means a little less slippage and better blade efficiency.
However, the parts list for your boat calls for 16 X 15 or 16 X 16 wheels, not 16 X 12's. I looked for the online prop chart to confirm this, but it seems that it is no longer available.
One other thing you should check is the carburetor jetting on your engines. While a 2500 ft altitude does not seem like much, it can mead a drop of about 10% in the output of your engines. The reason is because the air at altitude is less dense which makes the engine run rich. Smaller main jets are required to get the mixture back where it needs to be to get full power from the engines.
Hope that helps..............
