Ethanol gas (E10) works fine in my car so it should be fine for my boat, too.
Cars go through gas much faster than most boats. You probably fill up your car once a week or so.
But ethanol's Achilles heel is that it's hygroscopic, meaning it absorbs water.
Car fuel systems are closed and under slight pressure, meaning they absorb very little water, and any small amount that gets in will just burn through the engine until it's replaced by fresh fuel next week. But most boat fuel tanks are open to the atmosphere. That little vent you see in your hull allows air to replace fuel as it's used, but it's also an inlet for moisture. A deck fill that even slightly leaks can put a lot of water in your boat's fuel. As enough water gets into your boat's gas tank, the ethanol combines with it, and when there is enough, the ethanol/water mixture separates to the bottom of the tank, right where the fuel pickup is. The result is a stalling — or even a damaged — engine.
Sailboats have the right of way.
Lots of powerboat operators may be gleeful to see this myth exposed in print, but don't get too smug because powerboats are still behind sailboats most of the time in the pecking order. But sailboats aren't even halfway up the list. Without getting into too much detail, the pecking order from least to highest privilege is seaplane, power-driven vessel (this means your sailboat, if your engine is on, even if not in gear), sailboat, fishing vessel (commercial, not recreational), vessel constrained by draft (think ship in a narrow channel), vessel restricted in ability to maneuver (such as a dredge or vessel servicing a buoy), and at the top, a vessel not under command (this could be a vessel drifting due to an engine failure or one that's flooding or on fire).
But this is not a hard-and-fast "no exceptions" statement of the rules.
Older boats are money pits.
This one may have a ring of truth to it for anyone who's ever tried to restore a "classic." But a well-cared-for older boat doesn't have to cost an arm and leg to maintain and may actually be cheaper to keep than a newer boat.
Systems (e.g., plumbing, wiring) are less sophisticated, which means someone who's handy can often do more maintenance and repairs than he or she could on a newer boat with computer controls, electric doodads, and complex engines.
The best older boats to hang onto are often those that were made in large numbers; parts are often easily available and there is usually a large group of enthusiastic supporters online who are willing to share money-saving parts-sourcing and repair tips.