alpha 1 gen 1 impeller base differences

[stang32]

ok, i bought a new impeller kit with base, pulled the base off only to find out the one i bought does not fit, this drive has a pin on the unit that the new base will not fit over,
the 2nd base i bought has the section cut out to fit the little pin but the base does not fit in the hole to keep the oil in, the base has a smaller circumference

 

[alldodge]

For me I'm going to need pics

 

[achris]

Are you sure it's an Alpha One, and not an R drive? Got a serial number? (Externally they look pretty much the same)

 

[Bt Doctur]

does the lower driveshaft have a preload oin on top

 

[Bt Doctur]

If you have a pre load pin on the lower driveshaft you use the MC-1 base, if there is no preload pin you use the R,MR, Alpha1. this is R,MR, Alpha 1

 

[Bt Doctur]

this is the mc1 that uses a preload pin in the driveshaft

 

[stang32]

no, the driveshaft does not have a preload pin. i am working on 2 drives, one is from a 1990 merc, serial # oc837937, that drive takes base

https://i.ebayimg.com/images/g/1UAAAOSwCPdZ662r/s-l1600.jpg

the base shown above has a notch in it to fit around a little button/dowl pin on the lower case.

the other drive is an 89 counter rotating drive and i got the info based on serial # on top of the flame arrester is oc630165, who knows wha has happened to this boat in 30 years though.

that one has a 2 piece base and the piece that the o ring sits on is smaller than the above photo
the unit from the 89 does not have a button/pin on the lower case

 

[Bt Doctur]

the serial number says it uses base 46-44292A3 .Same base as the Alpha 1 and Alpha MR
No base is 2 piece My guess is that this part broke free from the base and is in the drive

 

[achris]

If you have a pre load pin on the lower driveshaft you use the MC-1 base, if there is no preload pin you use the R,MR, Alpha1. this is R,MR, Alpha 1

Pre-load pin is on MC1 and R.... MR and Alpha One don't have a pre-load pin...

Also remember that lower housings can be swapped around. You may have a MR upper, but an R lower....It's the upper housing that has the serial number on it.....