Mercruiser pre-alpha swap

[jfitz392]

I have a 1972 Mercruiser 120hp 4 cyl (S/N 411558) the current stern drive is "pre-alpha" and is badly corroded. I would like to replace the stern drive with a used Mercruiser Alpha Gen 1 (also 4 cyl). Is this do-able? I get that the trim indicator system is different but will the replacement stern drive line up with the bolt holes on the current transom plate Will the current outdrives bolt to the Alpha gimbal housing? These may seem like simple questions but I am treading new ground here.​

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Thanks​

 

[alldodge]

Hey @Bt Doctur can you advise

 

[Scott06]

I have a 1972 Mercruiser 120hp 4 cyl (S/N 411558) the current stern drive is "pre-alpha" and is badly corroded. I would like to replace the stern drive with a used Mercruiser Alpha Gen 1 (also 4 cyl). Is this do-able? I get that the trim indicator system is different but will the replacement stern drive line up with the bolt holes on the current transom plate Will the current outdrives bolt to the Alpha gimbal housing? These may seem like simple questions but I am treading new ground here.​

​

Thanks​

Are you talking about swapping transom assemblies as well as drives? Or just bolting up the newer gen one drive to the mc1 bellhousing? The drive should be a bolt on to the existing bellhousing.
if you want to swap transom assemblies that can be done but is more involved as they changed the rear motor mount spacing in 1981 oe so…

 

[achris]

I have a 1972 Mercruiser 120hp 4 cyl (S/N 411558) the current stern drive is "pre-alpha"​

Nope, it's a Mercruiser -1 drive (MC-1 for short). Merc never made a drive called 'pre-alpha'...

... I would like to replace the stern drive with a used Mercruiser Alpha Gen 1 (also 4 cyl). Is this do-able? ...​

Yes. An Alpha One will bolt straight on. You will need to check the shift cable adjustment, but other than that, it's plug and pray.

Chris.......

 

[jfitz392]

OK, thanks

 

[nola mike]

Nope, it's a Mercruiser -1 drive (MC-1 for short). Merc never made a drive called 'pre-alpha'...

Yes. An Alpha One will bolt straight on. You will need to check the shift cable adjustment, but other than that, it's plug and pray.

Chris.......

Shorter input shaft on the mc-1, no?

 

[achris]

Shorter input shaft on the mc-1, no?

Oh, yes. @jfitz392 You'll need to swap the input yoke.

Chris...

 

[jfitz392]

OK......I am pretty much clueless here. By input yoke are you talking about on the outdrive? Do you mean this part: 39385A 1 - Yoke Assembly?

 

[Eric 3.7LX Alpha 1]

OK......I am pretty much clueless here. By input yoke are you talking about on the outdrive? Do you mean this part: 39385A 1 - Yoke Assembly?

Yes and Yes. The part of the drive that the Ujoints are attached to, and the other end slides into the coupler in the back of the engine.

 

[jfitz392]

Got it, thanks again