Should I replace the dynaplate?

I have a 6 x18 dynaplate on a trawler that sometime in the past was painted. Supposedly rendering it useless. I sanded the paint off it and left it attached knowing the sanding is not supposed to correct the painting. I have not noticed any adverse effects but then again would I recognize them since it has been in this state since I outed the boat. Replacement is on my list for this season but a dynaplate that size is in the mid 600 dollar range.
Ken

Ask a marine electrician or electronics repair specialist.

What about removal and then sandblasting the surface heavily while off the boat..

What is it's purpose in your system? Is it being used for an SSB ground plane/counterpoise? Is it for lightning protection? Is your boat bonded? Do you have a hull anode tied to the bonding system?

Maybe soaking in paint stripper followed by high-pressure air blasts from behind ...

I appears to be part of the bonding system. I have been lead to believe there is no way to clean the pores after it has been painted. It definately is not part of a ground plane for SSB antenna. I have thought of putting a ham rig in and would then use that as a ground plane. As far as lightning protection I am not sure. I guess I will have to investigate the methods of lighting protection that can be employed and see if this fits. All I do know is the bonding system is attached to it and I do not have and corrosion problems. Does this mean the thing is working?

It is working, but at a reduced capacity. The idea behind those is that the porosity allows more exposed surface area, making the plate appear much larger than it is in reality.
If you aren’t going to put in a ssb anytime soon, I wouldn’t bother replacing it. It will still function as a central ground/bond point.