"VM"- I own an 89 311-SR1 and mine came with 23 inch Mirage. I'm running 454 mags basically stock. After speaking with Hydromotive extensively I swapped to a pair of 24 inch Hydromotive Quad IV Intimidators. These props add stern lift and our boats are ass heavy. The boat now rides higher out of the water than with the Mirage. On GPS I saw a solid 6/7 mph gain at cruise (3300) and 3 mph on the top end. By getting the rear end up out of the water it is creating much less drag, kind of like raising the "x" demension. The guys at Hydromotive were great, they told me exactly what I could expect and why. They were right on the money. The cruise increase was just tremendous, as that's where we spend most of out time anyway. I know that generally when you swap from a 3 to a 4 blade prop you downsize pitch, but the drag was reduced so much that it allowed me to go up one size. I understand the new 5 blades are even better. Give Hydromotive a call. They advertise in all the major performance boat magazines. You won't be disappointed.