1985 Johnson 50hp replaced with 1991

[KellerS]

I am looking to replace my powerhead on my 1985 Johnson 50HP, I have an opportunity to purchase a 1991 Johnson 50hp. I was told that the components are different but it would bolt up with no problems. Am I being told incorrectly? Advice please.

Thanks in advance

Scott

[boats.net]

Unfortunately I do not have access to the detailed information of the block to tell if they will bolt up, however they are different motors (components)