I have been reading all the post about premium blend gear lube.
I have a 1964 johnson 90hp with electro-shift, is there a replacment gear oil
suitable for me?
You need special gear lube for that electric shift. It was called "Type C" for years. Why not google it and see if there is a modern replacement. I would also think a Johnnyrude dealer would have some.....
You can also use trans fluid temporarily intill correct fluid is installed, But I don't recommend you use it for any length of time. Maybe enough to see if it's operating properly! Good luck