I wouldn’t be too keen to disregard the existing motor.
It will remain part of the character of your boat,very important.
It is so easy to throw out the old and put in a new one,which is not always the answer.
I have a motor in one of my corvette’s that is 40 years old ..It’s as good as new.
Yes,! If is giving you troubles and you can’t get parts,then,when that occurs,replace.
As I said,and Doug reiterated give it a good session of TLC and see how it goes.
It’s all about, preserving what you have in many cases.