(Richard Casady) wrote in
:

you can't change anything
out, like you can a prop or gearbox.

Simply not true. There are the same kinds of impeller pitches as there are
props.

http://solas.com/products/pwc/impeller/impeller.htm

Older jetboats also have different impeller pitches available but are
getting hard to find. Try a prop shop in your area...