Re: 150 evinrude
It may or may not increase your speed but it will increase acceleration because of the 2:1 ratio. To increase speed you may have to go to a larger pitch prop. You may have to drop the motor some on the jackplate to get the right water pressure unless it's a low water pick up gearcase.
The exhaust being restricted will depend on what rpm you're looking for. There is a very simple way to open it but without dry stacking the mid section that may hurt performance too. It all depends on your hull and set up.
