View Full Version : prop for a alpha 1 generation 1 outdrive

01-01-2017, 08:23 PM
I'm looking for the correct pitch prop to give me better high end speed. my boat is a 1969 18' barrel back with a 350 chevy engine with a mercury alpha 1 outdrive. my current prop was on there at purchase and the pitch is unknown. but its an older aluminum prop that is really beat up. anyone know what prop pitch could achieve max MPH on my boat?

thanks for looking pete

01-01-2017, 08:47 PM
We need more info to help. What HP does your motor make, and what drive ratio do you have? Can you figure out your current prop pitch? What RPM are you making now?

01-01-2017, 09:00 PM
horsepower is 255, I cant read the current pitch as mentioned the prop is beat up. at 5,000 rpm I'm doing 58 MPH. I'm not sure of the drive rations, I take it that that's the gear ratios in the alpha drive?


01-01-2017, 09:10 PM
Yes, sorry, typo: looking for gear ratio in the drive.

01-01-2017, 09:24 PM
gear ratio is 1.47/ 20-22, pete

Pat McPherson
01-04-2017, 11:47 AM
I'd try a 21P or 23P Turbo 1 or Merc Mirage and go from there.

01-04-2017, 06:31 PM
Agreed, and if at 255HP, thinking I'd try the 21 pitch first. With a solid GPS speed on that and an RPM measure, that'd be a decent guess at right and a big help to dial in.

01-04-2017, 07:55 PM
ok I will try those and let you know how it goes, thanks for all your help

peter j

01-05-2017, 12:25 AM
Sure, keep us posted. Also, one other thought came to mind: if top end is your goal, I'd bet the Mirage 3-blade will be the fastest prop you find. (The 3-blade Turbo I'd expect to be a hair slower and harder to twist, requiring about 1" less pitch to get your RPM right. You might prefer the handling though, and better cruise efficiency.)

joseph m. hahnl
01-05-2017, 06:34 PM
Dump the aluminum prop. They don't work well with V8s . A 21 Mirage which is stainless should put you between 4600 and 5000 RPM The 69 barrel back has the lifting strake running all the way to the transom doesn't it?

01-05-2017, 07:46 PM
BBLADES has the try before you buy program.:yes: