Fuel is the system that burns boats. H-24 is the gasoline standard and H-33 its diesel counterpart. For gasoline boats, much of the same ground is also covered by US federal law, which is public and mandatory for builders.
What they cover
ABYC lists H-24 as Gasoline (Petrol) Fuel Systems and H-33 as Diesel Fuel Systems. In our words: the whole fuel system, fill, vent, tank, lines, valves, pumps and filters, how it's built and installed, and the hose that connects it.
What surveyors check against them
Hose type and marking. USCG fuel hose comes in four types: A has passed a two and a half minute burn test, 1 lets less vapour through the wall than 2. For gasoline, the supply line to the engine is Type A1, with B1 allowed where the drainage test is met; vent and fill lines A1 or A2, and H-24 asks for A2 on fill hoses inside engine compartments. Diesel systems under H-33 can use any of the four types for fill and vent. Approved hose is marked with its type, maker and date at intervals of 12 inches or less. See fuel hose type and age.
Siphon protection on gasoline. A line that runs below the tank top needs an anti-siphon valve, an electric stop valve or the manual shutoff option. See missing anti-siphon valve.
Tank and fittings. Corrosion, leaks, and fittings compatible with the tank. See fuel tank corrosion.
Citing them in a finding
"Replace the unmarked supply hose with USCG Type A1 fuel hose, ABYC H-24." For a diesel boat, cite H-33. For a gasoline leak, the finding opens with "do not run the engine".