Just an idea
I was having a problem with my compressor either not engaging or cutting out intermittently on a 1987 190 2.3-16. It ended up being the connection on the compressor. There was a 3 prong connection on the back side. It has a male/female pin set up and the female connectors had become loose. I took a needle nose and squeezed them shut a little and have not had a problem since.
Itís worth a shot.