9.9 low rpm when gear engaged

[whitesfam]

My 9.9 (remote controls) idles fine and will rev as expected when in neutral; but when it is shifted into forward or reverse, there is no increase in rpm even with throttle/shift all the way forward or back. Gas line filter is clean, and carb idle and fuel mix were adjusted early in the summer. Fuel tank vent is OK, and throttle cable seems to work fine. Suggestions?

[rodbolt17]

as you increase the throttle, does the linkage at the engine move correctly??

[whitesfam]

Linkage at the engine seems to have full range of motion, and operate smoothly.

[99yam40]

did you pull the cowling and silencer and make sure all parts are moving properly when problem shows up?

[whitesfam]

Yes--no visual evidence of any problem