I have a 16' Sylvan with a 50 HP Johnson Outboard. Previous owner bought a new prop for it and it is AWESOME! Lowers top end speed by a little (dont need it anyway) but much more power to get on plane.
For trolling it gets down to 2.2 and I use 1 sock to get to 1.6 and 2 socks to get to 1.1 MPH. No chasing as there is not that much pressure on the socks. I swear by this, it really works great for me.
I can also tow a 240lb guy on waterskis with no problem as more power out of the hole.