Alpha One Gen 2 Gear ratio

[dlogvine]

I was looking to replacing the outdrive for my 1993 Mercruiser 4.3 V6. The charts say that the correct gear ratio is 1.81 17/19 (I assume 17/19 ,means the number of teeth on the gears?) The outdrive I found on ebay it comes with the following description

Alpha One Gen II with 24 24 gear. Good shape. Came off a 3.0. Mec.​

From an online gear ratio chart the only 24/24 gear ratio I found was for V8 engines. Could it be possible that 24/24 belongs to the 3.0 Mercruiser?
And the other question is what are the consequences of using the wrong gear ratio outdrive?
Thank you

 

[harringtondav]

You are correct with the gear tooth count and ratio on your. My 4.3 LX 180 hp uses the same drive. The 24-24 drive is a 1.62:1. My bud's 350 mag uses this. The 1.83 drive turns the prop shaft at 2622 rpm at and engine speed of 4800. The 1.62:1 gives 2923 prop shaft rpm at 4800 engine rpm. This allows the more powerful V8 to achieve higher top planing speed. I believe my bud uses a 24-25 pitch prop, I use 21-23.

So the 1.62 drive will work fine for you. But you will have to reduce the pitch of your prop considerably to get 4800 max engine rpm at WOT. There are many prop sizing applications out there to get you close. My guess is you'll have to reduce your current prop pitch by 2". 18 to 16, 17 to 15 etc.

 

[JoLin]

Something's a little screwy, I think. A 1.62 gear ratio sounds right for a 5.7, but the seller of the drive says it came off a 3.0, which uses a 1.94 ratio.

The usual (all the ones I know of) drive ratio for a 4.3 is 1.81/1.84. A 1.94 on a 4.3 motor would require a prop with more pitch, a 1.62 would require a prop with less pitch.

I think dlogvine needs to confirm exactly what that drive ratio is- 1.62 (from a 5.7) or 1.94 (from a 3.0)

My .02

 

[Rick Stephens]

If it came off a 3.0L it is either 1.94 or 1.98. It may be too big a jump in prop pitch for a good running 4.3L. Could end up needing 25 pitch or higher.

 

[Fun Times]

They did do a 24/24 gear count for the 4 cylinders as well.
https://info.nuwavemarine.com/mercruiser-alpha-outdrive-gear-tooth-chart/
https://www.seilermarine.com/info/mercruiser-drive-ratio-chart.php

Mercruiser Alpha 1 Gen 2 (1991 & Newer)

3 Liter	130	3.0/181	4	2.0	24-24	1998-2005
3 Liter	130	3.0/181	4	1.94	20-24	1991-2005
4.3 Liter	175	4.3/262	6	1.81	17-19	1991-2005
5.0 Liter	230	5.0/305	8	1.61	24-24	1991-2005
5.7 Liter	260	5.7/350	8	1.47	20-22	1991-2005

Engine HP Liters/CID Cylinders Gear Ratio Tooth Count Year

 

[Mercperk]

This is not the proper place to ask being so much later but;
What would the purpose of running the 2.00 ratio on a 3.0l?
Better efficiency? Easier on the engine? For skiing/towing?
And for the life of me I cannot seem to figure out what is the difference between the 2.00 and the rest of the gearcases?
Is the gearcase shell different or just the gears?

 

[achris]

Old thread (rules are no posting to threads more than 90 days old unless you are the OP), please start your own question in a new thread.

Chris..
iboats mod team.