70HP Johnson 2-stroke hunting at WOT

70HP 1979 (I think) Johnson 2 stroke on a pontoon.
Stator just replaced by service folks.
Has always hunted (rpms increasing slightly and decreasing over a 1-2 second interval) at low throttle, but always smoothed out at mid to WOT. Have video of engine sound and RPM dial if interested.

Now its hunting by about 20 RPM (3600-3800) at WOT.

Fresh (no E) gas this season; always used no E, was stored with some gas but had marine stabilizer; new fuel/water separator installed with new gas hoses end of last season. No visible water at bottom of separator.

I'm thinking I have a carb cleaning project in my future?
Thinking about trying gas treatment (recommendations?) first?
Advice?

Thx much!
Tom

It should be running at 5000 / 5500 RPM at full throttle.-----Post actual compression values.----Does spark jump a gap of 3/8" on each lead ?-----Stop running the motor as it is now.-----A plugged carburetor can result in serious piston / cylinder damage.