Swap from 120 to alpha 1

[Jdip83]

While going thru my 120 I have found some issues that I feel I'm wasting my time or maybe just a little time consuming.
So I'm wondering what I would need todo to swap out the 120 and put in an alpha 1 because I can get a operational alpha for a decent price.

I have a 2.5L that I have gone thru and found that it is worth fixing.

So I am wondering what I need to swap
Whole motor
Bigger
Transom
Gimbal
Shift
Steering
And so on

Thanks guys

 

[thumpar]

Re: Swap from 120 to alpha 1

Alpha is a drive and 120 is a motor. What exactly are you looking at swapping. I have a 120 with alpha drive.

 

[Jdip83]

Well I want to swap the drive From a 120 to alpha

I think, if I can do it for cheaper than repairing my 120 drive now
The last pic is the shift shaft in the lower unit it's rusted in place and won't turn. But the unit is in drive.
I have a few other post asking questions about this drive.

 

[thumpar]

Re: Swap from 120 to alpha 1

Oh this boat again. Well a 120 is still not a drive. You have a early mercruiser drive. Not sure exactly what maybe a 1r or mr.

 

[achris]

Re: Swap from 120 to alpha 1

A complete Alpha One drive will bolt straight in. You will just need to change the input yoke. Use the one from your MC-1 drive ('120' is just the small sticker put on the drive to indicate the engine that's in front of it). It's about 1-1/2" shorter. Just make sure the Alpha One has the same ratio, 1.98:1....

 

[stonyloam]

Re: Swap from 120 to alpha 1

Looks like what you have now is not a drive, it is junk. If you can find an 120 (or 3.0 or 140) engine with a decent alpha 1 drive you should be able to replace what you have now. Good luck, looks like you will need it

 

[ziggy]

Re: Swap from 120 to alpha 1

yep, i can see why ya'd wanna replace that...

the way i get it is.
the major components of mc-1, 1r, 1mr, alpha1 are interchangeable. uppers and lowers. not internals. so that'll cover your 120 drive. i'm just assumin it's an older one that says 120 on it. i think the mc-1 days they did that. mine would be a 165. it's an mc-1. what you'd wanna be concerned with next would be the gear ratio. ya wanna got that the same as ya have. likely a 1.98:1.
don't forget to check out the sei stuff. .$1300 round abouts for new w/ warranty.. alpha1 copies..

 

[Jdip83]

A complete Alpha One drive will bolt straight in. You will just need to change the input yoke. Use the one from your MC-1 drive ('120' is just the small sticker put on the drive to indicate the engine that's in front of it). It's about 1-1/2" shorter. Just make sure the Alpha One has the same ratio, 1.98:1....

So take the yoke off my drive and put it on the new one

And thank you for explaining how the labeling works hat thought it was a 120 motor with a 120 drive
The book doesn't help much
How would I make sure its a 1:98:1 if I buy it from private party.

 

[Jdip83]

Oh this boat again. Well a 120 is still not a drive. You have a early mercruiser drive. Not sure exactly what maybe a 1r or mr.

Yep this one again
Least I can realize that I'm gonna dump money into a pos

 

[achris]

Re: Swap from 120 to alpha 1

S...How would I make sure its a 1:98:1 if I buy it from private party.

Either take the top cover off and count teeth, or count turns to the input shaft and to turns of the prop shaft... (19.8 turns of the input to 10 turns of the prop shaft)

Tooth count should be 20-24...

 

[ziggy]

Re: Swap from 120 to alpha 1

the attachments on gear ratio would be one way.
here's a c&P i got years ago from iboats.

How do I check gear drive ratio?

Do all these steps in order.
1. Shut off the battery switch
2. Pull the spark plugs out of the engine.
3. Put the shifter in forward.
4. Turn the engine till the prop starts turning, continue turning till the timing mark is at TDC.
5. Put a mark on the prop hub and the drive housing that align with each other.
6. Turn the engine by hand while someone watches the marks on the prop, and count the revolutions the crankshaft makes to turn the prop 1 complete revolution.
7. If it took 1.5 revolutions of the crankshaft, then you have a drive ratio of 1.5:1 which is what is needed for a small block V8. (a 260).

instead of crank revolutions, just use input shaft revolutions.

 

[achris]

Re: Swap from 120 to alpha 1

... Not sure exactly what maybe a 1r or mr.

Neither... It's an early MC-1. 2 tells I see in the photos.
1. 'ribs' on the side of the top box. Later 'flat tops' have smooth sides.
2. Cast-in water pick-ups. Later models have plastic inserts...

 

[ziggy]

Re: Swap from 120 to alpha 1

It's an early MC-1.

Cast-in water pick-ups. Later models have plastic inserts

cool, new id info for me... fwiw. my '75 has plastic inserts. Jdip83's must be earlier than that.. thanks achris... i do got the ribs too in '75 mc-1...

 

[Jdip83]

Yeah it is a very early 67'

Thank you

Any suggestions
On what would be the best for parts and so on
I just see that alpha 1 's on a lot of posts
Would any generation work or just 1st for straight bolt on and yoke swap and the correct ratio.

I found a alpha 1 on eBay for 400$ but am very sceptic on the price and not being able to touch it and I would hate to waste more money.

 

[achris]

Re: Swap from 120 to alpha 1

Any MC-1 (1963-1982), R (1983-1984), MR (1985), Alpha One (1986-1990) drive will fit. From 1991 the drive is Alpha One Gen II, that will not fit....

 

[achris]

Re: Swap from 120 to alpha 1

I found a alpha 1 on eBay for 400$ but am very sceptic on the price and not being able to touch it and I would hate to waste more money.

This one? http://www.ebay.com/itm/Mercruiser-..._Accessories_Gear&vxp=mtr&hash=item1c1f74b9c2 ... Looks ok, but it's probably an MR, not an Alpha One. See if you can get a serial number from him. With that we can verify the year.

 

[starsnstripers]

Re: Swap from 120 to alpha 1

Look in Craigslist under boats in your state, type Mercruiser drive in. Buy it local if you can and then you dont get taken. Also you can make sure you have the correct ratio.

 

[starsnstripers]

Re: Swap from 120 to alpha 1

Here ya go. You'll have a 3.0 to upgrade and spare parts. Might be a shift cable problem with it but says reverse issue with the drive. http://sfbay.craigslist.org/sby/boa/2725561505.html