choosing a lower unit

[richny]

Hi, I have a 1992 mercruiser 4.3 with an alpha 1 gen 2 outdrive. looking into a new lower unit and was told any lower from a 1990 and up will fit. Thought I need to have one with a specific gear ratio...1.81:1 Any thoughts, ideas or insight is appreciated.

 

[thumpar]

Most 1991 and up will be a Gen II. The ratio is done in the upper half. When you say lower do you mean the whole drive or just the actual lower half of the drive?

 

[richny]

Just the actual lower unit. Looking at SEI they sell lower units with different gear ratios. so not sure if I had to buy one of those or any lower unit from any 91 up.

 

[thumpar]

Which do you need? One is a drive the other is the lower half. If you get the whole drive you need to get the right ratio. If you get just the lower you only need to make sure it is NOT the one for a 2 or 2.4 ratio.

 

[richny]

yep just the lower half. So looks like you answered my question. Thanks!

Makes me wonder why SEI sells lower halfs (not the whole drive) specifying different ratios?

 

[thumpar]

yep just the lower half. So looks like you answered my question. Thanks!

Makes me wonder why SEI sells lower halfs (not the whole drive) specifying different ratios?

There are 2 on the Gen II drives. One is for all the regular ratios and the other is just for 2.0 and 2.4. The 2.0 and 2.4 are not as common but they are different. If you look at the ratio chart with teeth count you will see why.

 

[QBhoy]

Sometimes stamped at the top of the drive what the ratio is...in case you are still in doubt