Silverton and Mainship were sister companies; build quality, systems, etc. are similar. Solid Chevrolet/Ford/Dodge category.
There's a Silverton Owners Club online (silvertonclub.com, modest annual fee) and there's Mainship owners group on Yahoo. I know there are several Silverton 40 MY owners in the SOC and they could answer questions.
The Mainship 40 Sedan you mention is not a trawler
? If that's the case, it would have been built sometime between '88-1995-ish (plus/minus) during the period where Mainship lost
their original focus (likely due to market forces; trawlers weren't so cool then.)
Don't know anything about the CC 381.