Gear ratios? replacing Sterndrive

duster22

Seaman Apprentice
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Jul 9, 2009
Messages
40
Hey, I have a 1983 140 3.0 merc with a alpha one gen 1 drive. What i am wondering is how to find the gear ratio? i broke the skeg and the prop and when i turn the prop it wiggles a bit. So i decided its the end of the season ill just put a used one in. I found a 1.83 ratio i was wondering if that would work? Any input would help alot.
Thanks,
Ryan

ps. The steps i should do and tips i should look out for to change the whole unit would be great. thanks again
 

brisboats

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Jul 13, 2006
Messages
31
Re: Gear ratios? replacing Sterndrive

Your ratio should be 1:98:1 with a 3.0. You can pull the top cover and count the teeth on the gear set. I think you found a 1:84:1 typically the gear ratio of the 470 series. That may work for you with a lower pitch propeller. Ideally you want the 1:98:1.
 

jtybt

Senior Chief Petty Officer
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Aug 5, 2009
Messages
730
Re: Gear ratios? replacing Sterndrive

Prop shaft on alpha's move in and out a bit but shouldn't wiggle side to side. If it does, check the drive oil for water contamination.
 

duster22

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Jul 9, 2009
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40
Re: Gear ratios? replacing Sterndrive

Could ripping the prop (aluminum) really bad bent the shaft? ill put some pictures up soon and possible a video of the wiggle.

And i will check the oil. And would putting on the 1.84 affect my performance. im kinda new i dont know how the ratios work or anything at all.

thanks ryan
 

Bondo

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Re: Gear ratios? replacing Sterndrive

And would putting on the 1.84 affect my performance. im kinda new i dont know how the ratios work or anything at all.

Ayuh,... The boat will be a Dog that don't wanta Run with Anything but the 1.98:1 ratio....
 

duster22

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Jul 9, 2009
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Re: Gear ratios? replacing Sterndrive

okay thanks ill get the pictures and video by the end of the day. maybe you guys can tell me if its fixable. i also have insurance. but dont want the deductable
 

Don S

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Aug 31, 2004
Messages
62,321
Re: Gear ratios? replacing Sterndrive

The shaft looks bent, the OEM service manual will show you how to check it and find out how much.
Doesn't really sound good either. Have you checked the gear lube (aka changed it)
Forget the 1.84, Won't work and you will hate it. They have different gear ratios for a reason.
 

duster22

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Jul 9, 2009
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Re: Gear ratios? replacing Sterndrive

the gear oil was changed less then 20 hours of use. Could i have damaged gears? any test i can do for that?
 

Don S

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Re: Gear ratios? replacing Sterndrive

the gear oil was changed less then 20 hours of use. Could i have damaged gears? any test i can do for that?

Could care less what the gear lube looked like 20 hours ago, the question is, what does it look like NOW!!!!

Sure you could damage gears, It happens all the times when props get mangled like that.
 

duster22

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Jul 9, 2009
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Re: Gear ratios? replacing Sterndrive

sorry i dont know what i was thinking. i just took a sample out and it looks fine its green. what colour would it be if there was water in there? i figure i should take it all out to really know.
 

duster22

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Jul 9, 2009
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Re: Gear ratios? replacing Sterndrive

there is fine bronze and milky streams in the oil. So i replacing it is a must. Im looking at a 1.94 for 1200

What do you guys think?
Would this work?
My dad's the one who is going to put it in. I am only 17. Is there any tips or things to look out for when removing and replacing sterndrive?
Thanks, Ryan
 

Bondo

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Joined
Apr 17, 2002
Messages
70,465
Re: Gear ratios? replacing Sterndrive

there is fine bronze and milky streams in the oil. So i replacing it is a must. Im looking at a 1.94 for 1200$ brand new

What do you guys think?
Would this work?

My dad's the one who is going to put it in. I am only 17. Is there any tips or things to look out for when removing and replacing sterndrive?
Thanks, Ryan

Ayuh,....

Don't you think you might want to Help support this forum you're doing all your Learning at,..??..??

You probably otta delete that link to a Competitor's website.... The Mod.'s will when they find it,..
iboats lists the Same outdrive for $5.00 Less....
Yes,... It's the 1 that fits Your Boat...
 

duster22

Seaman Apprentice
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Jul 9, 2009
Messages
40
Re: Gear ratios? replacing Sterndrive

whats the chances of both upper and lower gears get stripped?
 

duster22

Seaman Apprentice
Joined
Jul 9, 2009
Messages
40
Re: Gear ratios? replacing Sterndrive

okay i think my upper is okay but just to make sure ill need to take the top part off. Does anyone know where to find the tool for that? i cant seem to find it on i boat.
 

Bondo

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Re: Gear ratios? replacing Sterndrive

Does anyone know where to find the tool for that?

It's a 3/8" or 7/16" 12 point socket.... Nothin' Special....
 

hande

Cadet
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Aug 5, 2009
Messages
8
Re: Gear ratios? replacing Sterndrive

Thanks for the great info posted here. My question is along the same line as Duster22. I have A 1984 470 with what must be the m/r/alpha 1. The drive was run without lube and the the top set of gears are grinding and done for. The bottom just needs cleaned. I 've been looking at several top sections on Ebay but most of them just tell what kind of boat engine they came off of. I assume as long as it is a alpha gen 1 it will match up with my boat and the bottom section. But unless someone lists a 470 how would I know which one will be a good match as far as gear ratios.

Thanks for any help
 
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