Wondering if anyone ever messes with this to try and get a little more out of there outboards? I have a 70hp yamaha that tops at 42mph but you can tell its restricted. Any thoughts?

Check with a tach to make sure you are still within safe operating RPM range. It might require a prop change and also affect your warranty if there still is one!

Jeff

How can you tell it's restricted?

In any case, it's not a good idea to "modify" any engine to put out more power unless you also upgrade the reciprocating components to safely handle the horsepower increase.

You can buy superchargers to put on your vehicle, car or pickup, that will substantially boost the horsepower. The question is, will the crank, rods, pistons, etc., safely handle the increased horsepower? They may initially handle it, but for how long?