The best way to get traffic going here is to have some interesting conversations going. You need to get some people who like to talk (write). For every person who posts, there are probably 20 who just read.
I think your method of giving small "awards" to people for posting
a certain number of messages is a great idea. Keep promoting it. Maybe think of other benefits which you can give people who post.
I don't think advertising is a good idea, way too expensive for minimal return. People will find the site and visit if there is something interesting to read.
You might try going through the websites at cruisenews.net and asking if the webmasters would be willing to answer questions about a geographical area, or a boat
type, or about certain type of equipment
Try having a featured subject every few days with an "expert" moderator answering questions and taking comments. Post a profile of the moderator ahead of time so people can see what their expertise is. Make a schedule and post it on the main page in a prominent place: for example, if I see that someone is going to be answering questions about sailing in Chile
(for example) and I am interested in that subject, I would make a point of stopping by and asking a few questions during the day or week that the expert will be answering questions.
If you need ideas for subjects to discuss, just take a look at back issues of sailing magazines and see what has been popular in the past. You could be doing this in each of your thread categories. Another way to find subjects is to ask people what their expertise is and focus in on what they have to offer. It is important to focus on very specific subjects that are of interest to many people. Sometimes you can post a somewhat contentious opinion as a thread starter and see where it goes, although I think that using hot subjects to increase traffic is not the best way to maintain quality visitors.
I think the key to getting traffic here is to have these pre-scheduled discussion threads with specific topics that people are interested in and to treat the discussions as if they were magazine articles, with links to the threads on the homepage. Promote next month's discussions in order to draw repeat traffic.
That would be creating an interactive magazine, the Slashdot type of online publication which has been so popular in other subject categories.
Sailnet sends out an email
every couple of weeks with articles on sailing subjects. I usually delete spam, but I always check out the articles and have founds some very good articles. You might want to have a monthly email
newsletter on request which would provide easy links to the featured discussions for that month.
Eham.net has a "emagazine" front page, with links to "articles" which are really just discussion threads on a specific subject. I think that the editors start some of the threads, or they select hot threads, and put a text link from the main page, and by doing so they have created a magazine instead of just a forum.