Replacing '77 Alpha One Outdrive with mid-80's Alpha-One outdrive

[jfoulk84]

I recently purchased a 1977 Mark Twain V-Sonic I/O with a Mercruiser 165. As it turns out, the stern drive is completely locked up (shaft/prop won't budge). There was a lot of rust inside of the gimbal housing (to the point that the bearing won't even turn). I found someone local with a complete setup gimbal housing, transom plate, stern drive, etc... off of a mid-80's Mark Twain that had a 140 in it. The gear ratio on his is 1.98. As I understand it, the gear ratio on my '77 is 1.62 or 1.65.

I understand that this large of a gap in the ratio is not a good idea, but I'm confused on something. On the following chart, it lists the 165 twice, for two year ranges, with two different ratios (and obviously, two different stern drive models).

So, is this more dependent on the engine or the stern drive year? Would I be okay with the higher ratio stern drive on my motor, or should I hold out for a 1.65?

Thanks.

 

[Bondo]

Ayuh,.... You'll run into several issues with that swap,....

The 165hp is listed twice, as there's the 165hp, I6, 'n a 165hp I4,...

The rear motor mounts are very different, 'tween the '77 transom assembly, 'n the '80s transom assembly,....
The drive shaft Lengths change with the transom assemblies,...
The trim systems are different,....

'n dependin' on what pitch prop yer runnin' now, there probably ain't a prop with enough pitch to make up the differences in the gear ratios,...

 

[Alumarine]

Why don't you split your current drive to see if both halves are the problem.
That won't help with your question but might help source parts.