A blocked vent can ruin your cruise. This is my saga: Gauge read empty, tank fills up with 2 gals. Hmm gauge must be broken and tank full, right? Lets go for a short sail. Wrong! Shortly thereafter I ran out of fuel! Urrrrg. Sailed back to slip and added 5 gals; Bleed bleed bleed, and got things running. Fill tank? Not so fast-it would only hold 2.5 gals more. 7.5 gals in a 30 gal tank? What the..? Yesterday I added a measly 2 ga and the neck was full so I looked at the tank. Tank was swelled like a bloated catfish. Took off the vent hose and whooosh! So I removed the hose and fitting. It was clogged with spider/dirtdopper crap or something. After clearing the line (most in the elbow fitting a top) the tank sucked down the remaining diesel I had in can. Guage still barely moves above empty but I figure I only have approx 10 gal in a 30 gal tank. (this was on a Hunter 340)

Moral of this-if the gauge isnt working high to low, dont depend on the tank being full just because its wont take on any more fuel. Check your vent hose today