I have used the Amsoil Saber Synthetic at 100:1 in my 1988 Johnson 9.9 HP motor and it runs a lot smoother at slower trolling speeds, I troll between 1.7 MPH and 3 MPH.
When I started using this my outboard mechanic told me that this is the ONLY oil to use at 100:1 as my motor is rated at 50:1...