Ethanol and old fuel: what to check on the tank before you buy an older powerboat

On older powerboats, the fuel system causes more headaches than the engine itself. Ethanol-blended gas (E10) and time are the usual culprits, so the YachtBazar team always pokes at the tank first.

Why it matters: ethanol absorbs water and can separate in the tank (phase separation), and on some older boats it attacks fiberglass tanks and rubber lines, leaving gummy varnish that clogs filters and carbs. Fuel that's been sitting a season or two is suspect on its own.

What to check before you hand over money:

• Tank material and age. Older aluminum tanks corrode from the outside in, especially where they sit on foam or in a damp bilge. Pinholes leak slowly and are expensive to reach.

• Fuel lines and primer bulb. Cracked, hard, or sticky lines mean the system's been neglected.

• What's in the tank now. Old, dark, or sour-smelling fuel is a red flag. Ask when it was last filled and run.

• Filters. A water-separating filter and a recent change are good signs.

A good rule of thumb: budget for fresh fuel, new filters, and an inspection of lines on any boat that's been sitting. Run ethanol-free where you can find it, and don't let fuel age in the tank over winter.

What's bitten you on an older fuel system, and how did you sort it out?