Hi Tom! The best way to do that is give the forum a more specific focus and re-name it accordingly. We've always had it hanging off the edge of our site, kind of like a benign growth.
Even that is going to be a little bit problematic, as this forum requires a separate registration and the format is different. But... that would be the best way to cross-sell people over here.
Another thought: last year we developed a new forum for the TSBB crowd. It uses the same threading everyone here likes here, has some extra features and ties to a database instead of (gasp) flat files. We could modify the TSBB code to make the CSBB work from a regular SailboatOwners.com login. That would really help integration and traffic, I think.
Ultimately, word of mouth is the best way to grow a forum, but I'm afraid this 1990's format is always going to be limiting to some degree.