Poor cooling from 9 yr old Sanyo SR-1030S

I have a Sanyo SR-1030S 10cu foot top freezer refrigerator on my boat. I got it because it was the only unit that fit the space. Recently it only cools the freezer to 9 degrees above and the refrigerator to 45 degrees on the MAX setting. I changed out the thermostat and defrost timer but this did not help. The compressor cycles on and off about every 10 minutes or so. I opened up the panel at the back of the freezer and there is no ice and the fan is blowing. I pulled the unit out from the cabinet and the coils on the back are clean. I was concerned that there was an issue with air getting to the coils on the back of the unit however it performs the same in the middle of the galley. Prior to this it cooled well but had huge temperature swings.

I can't get a pro to come on the boat to fix it. They say their insurance won't let them. Any ideas where to look next? I am reasonably handy but I am running out of ideas.

thanks for any help

Frank