What is this upper unit? Pre-Alpha Gen 1?

[brewern]

It came off of my 1980 Rinkerbuilt 17' runabout. Was running a 25L 120HP GM 4 cylinder. I think the outdrive was from 1979. I understood it to be an Alpha One, Gen 1, but I found the link below here on the forum.
Outdrive Identification

And now I'm thinking it's a pre Alpha, Gen 1.

Any advice on what it is and the gearing ratio?




Thanks!

 

[Texasmark]

Re: What is this upper unit? Pre-Alpha Gen 1?

It came off of my 1980 Rinkerbuilt 17' runabout. Was running a 25L 120HP GM 4 cylinder. I think the outdrive was from 1979. I understood it to be an Alpha One, Gen 1, but I found the link below here on the forum.
Outdrive Identification

And now I'm thinking it's a pre Alpha, Gen 1.

Any advice on what it is and the gearing ratio?

View attachment 195073


Thanks!

you can get the gear ratio by merely counting the revs of the input shaft vs the drive shaft. Input will turn more revs than the drive shaft. If it turns 2 revs to one of the DS you have a 2:1 reduction. That would give you a prop velocity of 2000 rpm when the engine was purring along at 4000 rpms. I don't know what series it belongs to but someone on here will.

On your smoking congrats. I quit in 1988 after 30 years of smoking a pack a day. I bought a 1988 Ford P/U with a nice cloth interior and I didn't want to stink it up. So I just quit.

Mark

 

[Eric 3.7LX Alpha 1]

Re: What is this upper unit? Pre-Alpha Gen 1?

It's not a Mercruiser upper.... it's an aftermarket SEI 106, (Stern Drive Engineering) which is equivalent to the Alpha One. It's compatible with MC-1 to Alpha One.

If original it would have been the MC-1 drive. see the chart below:

And your ratio would/should be 1.98:1

You will have to be careful replacing the impeller (the lower housing anyways), the MC-1 has a preload pin at the top of the shaft, the Alpha One doesn't, they use different lower housings, same impeller and upper housing.

 

[achris]

Re: What is this upper unit? Pre-Alpha Gen 1?

It came off of my 1980 Rinkerbuilt 17' runabout. Was running a 25L 120HP GM 4 cylinder. I think the outdrive was from 1979. I understood it to be an Alpha One, Gen 1, but I found the link below here on the forum.
Outdrive Identification

And now I'm thinking it's a pre Alpha, Gen 1.

That's them!!!! There the ones who need shooting, and I'll happily pull the trigger myself.. ... Pre-Alpha.. Phooey!!!

Let me say this, AGAIN!!!! There is no such thing as a 'Pre-Alpha'... Please, ANYONE, find something in Merc genuine documentation that list a 'pre-alpha'.... Can't.. that's right... can't....

Now listen closely...

1968 to 1982 - drive was called 'MC-1'
1983 to 1984 - drive was called '1-R' (R for short)
1985 - drive was called 1-MR (MR for short)
1986 to 1991 - drive was called 'Alpha One'
1992 to now - drive is called 'Alpha One, Gen II'

OK.. rant over (for now).

Your drive is a knock-off, made by Sterndrive Engineering... If it's behind a 2.5l engine, then the ratio should have been 1.98:1

Chris.....
BTW, anyone who lists anything as 'pre-Alpha' clearly doesn't know what they are talking about, and should be avoided, period!

And for more information on the history of Mercruiser... -> Mercruiser Alpha ID and History - Download - 4shared - Don S

 

[haulnazz15]

Re: What is this upper unit? Pre-Alpha Gen 1?

That's an SE106 aftermarket replacement for the MC-1 through Alpha I drives. I would imagine you could find a drive ratio listed/stamped somewhere on the unit, but I'm not positive about that. If there is a serial number, you can use that and contact sterndrive engineering online or by phone to find out ratio what it was.

 

[brewern]

Re: What is this upper unit? Pre-Alpha Gen 1?

I'll never say pre-alpha again! LOL

Thank you all for your knowledge and insight! Hopefully this post will help others in the future.