Gracious people will offer to chip in somehow. I will usually take gas money from people if they are insistent, unless I know they can't really afford it, then I refuse.

However, as several have mentioned, there's wiping down the boat, setting it up and putting it away. People who are always there helping fold up the bimini, throw the rope out , etc are usually the same people who are offering gas money, bringing drinks and food for everyone. People without common courtesy don't chip in and lay out on the sundeck until it's their turn. The latter ones don't get invited back out.

I think what you are looking for is some appreciation that you are doing said 'gentlemen' a favor and you're not getting that appreciation. I wouldn't like it, either.

If we go out twice a week, I easily spend $800-1000 on the boat and truck just for gas. Then there's boards, ropes and other gear, the capital cost of the boat, insurance, storage and maintenance. All told, every trip to the lake is probably costing us anywhere from $200-500. Expecting your invited guests to acknowledge you sharing your toy is totally fine, whether you ever take a single dollar or not.