I'll type this in big letters just so its easier to see, not to accentuate any point I might have, or any other reason.
Its a hobby, not a for-profit business.
The difficulty is attracting new members has bugger-all to do with motor classes.
It has everything to do with what society as a whole is evolving into... generations where instant gratification with little or no effort is the expectation.
People are falling into water fountains in the mall because they can't take their eyes off the cell phone. Computer hockey game tournaments for cash prizes are a thing. You can get rich by making some stupid videos and putting them on Youtube, where your only talent is getting your idiocy watched by other idiots. But I digress......
The members that do exist have to do more work to inspire other people to join, whether they are young, old, somewhere in the middle, what ever. How to do that? Share knowledge. Reach out to new members in your area. Get motors out there for people to see so they have an opportunity to generate interest. Get them on the water so they can be seen in action where they belong - on the back of a boat, pushing you around so you and your passengers can have fun and enjoy the ride. Check with a local service club and ask if they would allow you to put on a presentation. Get out to the antique tractor and steam engine shows and put on a display. Make themselves available at the meets they attend to help out others with problem motors. If they have motors that haven't seen the light of day in 20 years, get them out to the shows or on a boat, or consider letting them go to other members who will. I think it would surprise you to find out how many AOMCI members do not do ANY of those things.
I don't think the problem is the number of members who are in the club. I think the problem is the number of members in the club who don't do any of the above, and are just along for the ride. They pay their dues, get the Outboarder and toss it if they don't see their name or picture in it, go to meets only occasionally to try and find something they want, then take it home where it's never seen again - or doll it up and put it on Ebay. They don't help out in any way, shape, or form, and they'll only call or show up if they want/need something. I have several nicknames for those folks, none of which are complimentary.
Average age of membership - its important to an extent. What's more important is that the current club members be responsible for contributing to two things 1) have more live members than dead ones, and 2) don't be one of the dead ones that don't do jack schitt to promote the club, its goals, or its values.
So what if the majority of members are older than 45? If they're 30-ish and not doing anything except take from the club what they can get without giving back in the way of promoting or participating, they're not helping any. The better question would be "how many of those members over the age of 45 got involved in the hobby BEFORE they were 45?" No doubt many of those people are "lifers", but I bet there are more than you think who were closing in on middle age before they really got wind of what antique outboards are all about.
I've been in the club since 1991 and have heard the "this club will be gone in 20 years" complaint more times than I care to think about. Its a hobby club, and there's going to be expansion and contraction. Interest will peak, then it will wane to a degree. Be that as it may, the AOMCI is way more stable than the stock market. When I joined I recall George Jacobs telling me there were about 2200 members. At one time I think we climbed up over 3000. Now its retracting to the point where its somewhere around 2500. It will probably contract some more. Do I worry about the club dying off because of it? Not really.
Remember the stated goals of the club. They're right in our logo. Its "preservation and restoration". Of the two, my belief is that preservation is more important. That is what we should be working on. Create all the classes you want. If its in the interests of preservation of motors, knowledge, and pertinent information, I'm all for it.
If its to expand the number of awards given out, or because judging categories will be "easier or more clear", then I dunno about that.
If somebody wants to do it the politically correct way, and put an actual motion in front of the EC so it can get voted one (which is what you're SUPPOSED to do, not expect them to put it to a vote just because it got posted on the Internet by some faceless/nameless entity - see what I mean about how too many are wanting instant gratification without doing the work?). One person has gone on the record of saying they asked the EC about the survey. Was he joined by anyone else? Numbers will get attention. Just sayin'....
Regarding the goals - you will always have a hard-core group who put the club and supporting its activities in the forefront. You'll have those who are along for the ride. As long as the AOMCI has more of the former, and less of the latter, the club and its goals WILL survive.
Simply put, we, as a group need to do a better job of promoting antiques and older motors, (and not so much the newer ones) for the single reason that if we don't, the interest in them WILL shrink to the point that it is going to be difficult to find homes for them when your time on this planet is over. I dread the day that somebody says "well I like your old Elto, but I got no room, I got my collection too full of 1980's/90's Mariners, Hondas, and Suzuki's to buy it".
Somehow, we have to instill the belief that the preservation and enjoyment of old iron will bring a person more satisfaction than sitting on their ass playing on their phone or computer.
Hope this helps.