Paul : very interested in this post.
Sea Eagle of 2004 vintage has a very similar problem.
Behind the ‘smoked glass’ panel, dirt has accumulated and is an eye sore.
Have tried to release the throttle control lever a few times with no success.
Have used ‘plus gas releasing agent’ and modified a bearing puller to ‘fit’ behind along with cable ties to clamp into position with the nut loosely in place.
No movement whatsoever !
My learned friend suggested applying heat, but I am nervous ! would use a thin metal heat shield behind.
Considered carefully cutting / splitting the smoked panel somehow above and below the control lever to allow removal, cleaning and replacing. This would also give extra bearing purchase on the puller.
Another option would be to cut the control lever, using a dremel, and replacing with plenty of marine grease for future removal.
I assume it has a spline arrangement.
So watching this post with a vested interest.