Going to a four-blade will help hole-shot and top end fuel economy. HOWEVER, it will cause issues if you slow troll live bait as in King Mac fishing. If you make the upgrade, you may need to drop a 5gal bucket over the side and tie it off to slow your boat to the proper bait speed. Live baits need to be able to swim, not be dragged thru the water. Ed Miller, HI-Tec Marine in Essex, Maryland is an expert on 3-blade to 4-blade change overs. WWW.HI-Techmarineservices.com.