Re: Interchangeability
Your question is way too general. If your talking between Johnsons and Evinrudes for any particular year, then they are almost completely interchangeable. If your talking between years, then it depends on the part being replaced. I was able to put the complete ignition system including the mounting bracket salvaged from a 1989 60hp Evinrude onto my 1978 70hp Johnson with only needing to grind down some unneeded bosses and adding 1/2 spacers under where the bracket mounts. The mounts for the later ignition bracket were there on my motor although not used by the original ignition system. All works great including the T&T relays that came on the bracket eliminating the need for a separate T&T relay box. Ended up with much better spark and much improved, more readily available, and less expensive modular design components. Also, put a 1988 gear case on the same motor. Sometime later they went to a finer spline at the top of the drive shaft, so can't use those. Added Tilt and Trim as well. Those units are compatible between many different horse power motors from 1978 to 1995. Changed to Fast Strike T&T in 1996 that is not backward compatible.
So, really depends on what your needing (or wanting) to replace.
