alpha1 outdrive gearing 1.62 or 1.47

[boatnik1]

new to this forum what gearing would lower rpms on a merc cruiser 220 hp. with a 13 3/4x21 stainless

 

[cptnmcluvin]

Re: alpha1 outdrive gearing 1.62 or 1.47

boatnik1,

My GT 205 has the 4.3 V6 merc MPI w/ 220 hp and a 1.62 ratio alpha one.
My Dads Sea Ray 210 BR has the 5.0 V8 merc EFI w/ 240 hp and a 1.62 ratio alpha one.
Usually the 1.47 ratio works well with the 5.7 V8 and larger V8 motors

The 1.62 ratio gears would run slightly higher RPMs than the 1.47 gears.

The larger V8 engines have enough low end torque to make use of the high 1.47 gear ratio.

 

[Bondo]

Re: alpha1 outdrive gearing 1.62 or 1.47

new to this forum what gearing would lower rpms on a merc cruiser 220 hp. with a 13 3/4x21 stainless

Ayuh,.... What motor,..?? What drive,..?? What are you tryin' to accomplish,..??

 

[boatnik1]

Re: alpha1 outdrive gearing 1.62 or 1.47

2012 searay 19 foot 220 hp. 4.3 mercruiser alpha 1, New boat stamped 1.62 gears on drive only hits 4300 rpm at wide open trottle. at 52 mph 13 3/4 inch by 21 pitch vegeance stainless 3 blade prop. with just me in boat. Same prop every one else got with the boat and they are at 53 mph at 4520 rpms with 4 guys and 50#s of gear. I am lugging it. have you ever heard of merc mis stamping a drive?? Dealer confirmed 4300 with digital tach. He's gonna pull it and do a tooth count.

 

[spdracr39]

Re: alpha1 outdrive gearing 1.62 or 1.47

Maybe the speedometer is off is that a gps speed ? Or maybe your friends speedometer or tach is off. Speedometer accuracy is not good enough to be compared at 1 mph difference. They are commonly off by 5 to 10 mph. What about the trim position? This can be a big factor. There are many variables to consider.

 

[boatnik1]

Re: alpha1 outdrive gearing 1.62 or 1.47

trimmed out gps speed and checked with digital tach.