Alpha outdrive upper and lower interchangeability

[crazy charlie]

I have twin 5.0 XL mercruisers with alpha drives 1988 .I have a spare lower unit.
A friend has a complete outdrive which looks same as mine however I believe it is from a 4cyl motor.The large tag on the back of the upper has a large 4 on it and 3.0 liter just under the 4. Is this outdrive useless to me or can I use the upper?? I know the lower is useless to me.Thanks Charlie

 

[Scott06]

I have twin 5.0 XL mercruisers with alpha drives 1988 .I have a spare lower unit.
A friend has a complete outdrive which looks same as mine however I believe it is from a 4cyl motor.The large tag on the back of the upper has a large 4 on it and 3.0 liter just under the 4. Is this outdrive useless to me or can I use the upper?? I know the lower is useless to me.Thanks Charlie

On alphas the gear ratio is done in the upper. So yes a 4 cylinder will have a 1.98:1 gear ratio Vs the likely 1.62:1 (could be a 1.50) you have. Soupper is useless. Lower would swap over, if you want a second spare…

 

[markhodges78]

Like Scott06 said upper is useless for your setup but the lower would be a direct replacement...

 

[crazy charlie]

Thanks guys!! I guess I had it backwards.Thanks again. Charlie