VelocityMike

I just bought a 1987 31' Formula. The boat has twin Big Blocks putting about 340hp per engine. They are mated to TRS drives thru velvet drive tannies. I'm an outobard guy and have never owned an i/o before.

My question is prop selection. To the best of my knowledge the boat has 23 pitch mirages on it but I am not sure. I would like to know what kind of props I should try in the spring and also what might fit on the TRS drive. Any advice would be great. Thanks!!!

Formula Outlaw

"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.

VelocityMike

Formula Outlaw...thanks for the advice. Very helpful.

Formula Outlaw

"VM" also, props interchange between TRS and Bravo 1 drives. I originally bought mine for an older 302 with TRS and ended up replacing that with the 311 with Bravo 1's. No problem. Slipped right on.