Mercruiser Alpha One Gen 1 Outdrive questions.

[Chemdawg]

Hello everyone. I have a question. My boat has an 87 3.0L Mercruiser with alpha one outdrive. Gen 1. This last summer the gears in the upper unit went bad. I puled it apart and cleaned out the upper case, and had the lower case rebuilt, by my local shop. I noticed some dings in the upper half that I wasn't happy with and was going to purchase a used unit that was at the shop. However, I know my unit has 20/24 gears for 1.94 ratio. This unit is a 1.84 ratio. Will this still work with my lower? I know it will change the ratio a bit, but will that make a big difference? It's an SEI upper unit in really good shape. I'm just not sure if it's a bolt on setup to my lower unit or if that gear ratio is too far off for my 3.0L.

Thanks in advance.
Pat

 

[Bt Doctur]

your going from a 120-130 Hp motor using 1.98 and installing a 170-220 Hp drive using 1.84
Doubtfull you will get to max rpm even with a prop change

 

[Chemdawg]

Thanks for the response. I did some research. Mine says it's a 1.94 but I found out the 1.98 is for a 3.0 as well. So I can use a 1.98 if I can find one. I believe the shop has one of those as well. Thanks for the info again. Pat

 

[achris]

The 1.84 unit will bolt right on. As the difference is very small and you may not even need a prop change. The revs will drop about 200, so if you're currently at the upper end of the range, stay with your current prop. If you're at the lower end, change to a prop 2" smaller.

Chris. ....