scott,
You should sharpen both the top and bottom of the grates. Sharpening and shimming the impeller will give you a noticable increase in power.
There is a ton of things you can do to the shoe of the pump to get more performance. I wont get into it here because its too hard to explain. But believe me it helps. Tom Sperb of Toms outboard is the man to talk to.
his # 1-503-653-8744.