Logo
FULL SITE MENU

choosing a new lower

R

richny02

New member
Hey all. hope someone can help as I'm a bit new to a sterndrive. I have a 1992 mercruiser 4.3 with an alpha 1 gen 2. Need a new lower and saw some from companies like SEI that have different ratios, mine being I believe a 1.81. Looking around I came across a couple people that had nice used ones for sale. They couldn't tell me what the ratio was on the units but said it didn't matter, that all lowers from 1990 and up will work. Is this true or should I stick with something I know has the correct ratio?
 
Buy genuine if you can find good used. Just look for same thing. Use your current serial number as shopping guide. If the folks who are selling these lumps can tell you the serial number on the drive, then you can look it up here on this website and find the ratio.

If you get different ratio, then your prop will be wrong and you will have to go through the process of finding the correct propeller.
 
HTML: 
info.nuwavemarine.com/advice-guidance/mercruiser-alpha-outdrive-gear-tooth-chart/
it was easier googling than digging around this place
 
Last edited:
makomark said:
On the alphas the gear ratio is determined in the Upper....the lowers are all the same ratio...
Click to expand...

That was true of the gen I

I dont believe it is 100% true of the gen II

But based on where he lives and at sea level and it is a 4.3 I would agree.


The lower has 2 different gear options,

Option 1 (most common) gives you 1.47:1, 1.62:1, 1.81:1 and 1.94:1. This is typical 99% of the time.


Option 2. 2:1 and 2.40:1. Which I believe is used on larger boats typically under powered like a 24 ft with a 5.7 260 hp. gives it a better whole shot to get on plane. The change to 2:1 and 2.4:1 is done in the lower when combined with the upper...........

How it all calculates is something someone else can figure out. Time for beer!
 
Last edited:
Back
Top