This has just starting happening on my boat too. I haven't had time to check it out yet. I was under the dash replacing a fuse and figured that I move something where it shouldn't be.
I pulled the new fuse that I had just installed but the trim gauge was still messed up. Have you found anything? My oil pressure gauge has always been flaky. It will look fine, and then when up to cruising rpms, it will jump up and down. My mechanic says the pressure checks out fine, it's the gauge that's wacked. Do the replacement gauges fix all this? Are the two panels plug compatible (i.e. and easy swap)?