There is not much you can do to make it faster without gutting the entire boat and starting from scratch.
This will be more expensive than starting out with a new faster boat.
I know the Radio Shack boats are a good price compared to an all out race boat, but the price soon becomes evident as the thrill wears off very quickly.
JAC, There are probly some cheap things you can do to add a little more speed, maybe ride pads and sharpen edges. Can you post picks of the boat or a link to some info on it.