Choosing between two 2 stroke oils for 1986 GT150 Johnson outboard engine

[Japanese]

40:1 has never gummed up mine. However, Sta-bil Marine 360 has a lot of anti-corrosion and cleaning agents in it, plus keeps the gas fresh for a couple of years.

It depends if you do trolling and for how long.
If you don't do trolling more oil won't gummed up or foul your spark plug.
Plus, TC-W3 oils don't have ash which is the main cause for dirtiness and fouled plugs.
The difference between 50:1 and 40:1 is just a spit or a tea spoon.

 

[SonofaBoomer]

I have been experimenting with oil ratios in my '94 Johnson. I have read that Johnson's like richer fuel ratios and they recommend a 50:1 oil ratio. It used to intermittently stall at low RPMs until I enriched the idle mixture by a 1/4 turn or so. I do a little bit of trolling but I run WOT to and from my spots so I figure 40:1 mixture is a good middle ground for protection and cleanliness.

I am not even sure what kind of oil these engines originally ran on but I am sure it wasn't as light as the tc-w3 that we have now.