When I replace mine I'm going with these. Had them on my old 28 saber. Extremely accurate however as I age I tend fly by feel it seems like...

I have the trim stiks and love em'!

When I get around to it I'm just going to use a slide potentiometer with an arduino. Should be about $15/drive/tab.

https://www.youtube.com/watch?v=Py26vaHFMZM&app=desktop

Or, you could go with a slide potentiometer and a segmented LED bar with the electronics on the bar eliminating the arduino for $15 more.

if were going to get a short cable inside the boat you could use a steering rudder indicator sender, looks like what you have drawn, have one on my gibson, made by teleflex

I have a brand new set of the merc electronic k plane actuators that I took off of my new k planes as I went with a cable. Not sure if they work for you but you can have them for free99. The wires were cut alittle short (still plenty of a pig tail hanging off them) by some jerk (me) before he realized he could have just taken them out of the thru hull. If you want them shoot me An address and Afew bucks shipping and they're yours.

pm sent