I have a carbureted 1998 Yamaha f50 4 stroke and I have been told it can be upgraded to a 70 by removing a restriction plate? This sounds very similar to the old evinrude’s where you could convert a 9.9 to a 15, 25 to a 35, 40 to a 55, 90 to a 115 ect. I also know the EFI Yamahas can be converted from a 50 to a 60. Not sure what would have to be done on the old Yamaha carbureted 4 strokes, but I’d be really interested to know as my current boat is just a hair underpowered.
