Re: Outdrive upgrade
Changing the gear ratio to a higher numeric can only affect acceleration, but that'd screw up top end and bring the engine above it's operating range. Results: Bad and slower.
Going to a lower numeric would stifle acceleration and drop the top end down so much that you'd be lugging the engine, and losing top end. Results: Horrible and slower.
Your only real chance to play with 'gears' is to play with props/designs/sizes.