Lower units

[Dougdad]

I hav a 1965 Merc. 500, 50hp, 4cyl.

I was woundering if anyone knows how many years they used the same lower unit casing? Even the 80's models look the same!
I need a whole assy. minus the gears, the shafts may even be salvagable. I found a 80's model complete lower for $50.00 on Ebay. Will it fit?

[boats.net]

No I'm not sure, I don't think the 80's models will work but not sure.

[Dougdad]

Lower units

Can you by chance tell me what years and hp will match? If I can widen the range in my search it may help.