Mercruiser 3.0 outdrive gear ratio?

Cmiller7609

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Joined
May 31, 2020
Messages
2
I have an 1985 3.0 SN A310892 that had the outdrive replaced with a pre alpha drive and it has the 1.81:1 gear ratio and I'm having troubles getting about 2,000 rpm at WOT. My question is does the 140hp 3.0 need the 1.98:1 gear ratio to achieve the 4600 rpm? I wouldn't think that the 1.81:1 would make that much of a difference? And I have done a compression test and all 4 cylinders are 120 to 125psi not the best but ok. Any help would be great thank you!
 

Bondo

Moderator
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Apr 17, 2002
Messages
71,308
My question is does the 140hp 3.0 need the 1.98:1 gear ratio to achieve the 4600 rpm?

Ayuh,...... Welcome Aboard,....... Yep, the 1.98:1 is the tallest gears the 3.0l can pull,......
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
I have an 1985 3.0 SN A310892 that had the outdrive replaced with a pre alpha drive and it has the 1.81:1 gear ratio and I'm having troubles getting about 2,000 rpm at WOT. My question is does the 140hp 3.0 need the 1.98:1 gear ratio to achieve the 4600 rpm? I wouldn't think that the 1.81:1 would make that much of a difference? And I have done a compression test and all 4 cylinders are 120 to 125psi not the best but ok. Any help would be great thank you!

Drop the prop porch down 2 or 4 inches and see how it goes...

Chris...
 

Cmiller7609

Recruit
Joined
May 31, 2020
Messages
2
I drop the pitch from 17 to 15 and it made a difference but not enough I guess I need to get an outdrive with the proper ratio to solve my problem.
 
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