Alright...my first "dumbest thing you've done on a boat" moment. The thing was reading above the red zone, figured I had 20-30 gallons...enough for 30min idle on each end and 20mins at 3k rpm. Well apparently not.
At least I ran out about 5 mins after coming through the inlet. Seemed weird that the port motor died at least 5mins worth of idle time before the starboard motor, so I wasn't sure it was fuel (gauge still wasnt reading empty). But when the starboard quit, I knew that had to be it.
So I drifted to a dock and got lucky that a buddy was coming through an inlet about 20mins away. He redirected and towed me to a gas dock. All they had was 93 so I only put enough to get back home.
I thought all was well until the water at the ramp shut off 10mins before it was supposed to, right as I was flushing the port motor. Didn't realize the water quit until I heard the impeller screaming for mercy...kinda sounded like when you throw a lobster in boiling water

Your tank(s) is/are angled to a point as they get to the bottom; not squared off. Think of it as looking at a martini glass from the side.

Fuel level senders are designed to work with squared off tanks; hence the not accurate reading as things get south of 1/2 tank(s) on the gauge(s).

You're not the first 311 owner to complain about this feature.

Don't feel bad Michael! After owning my boat for 8 years, I went out for a ride and a late lunch with the tank reading almost 3/4. Ended up hanging out at the restaurant longer than planned. When I started the boat for the return trip, I noticed the tank was below 1/2 now. So, I sped off to the nearest marina with fuel, only to find out they were closed! Surely with almost 1/2 tank I would get home! Well, as I neared the No Wake Zone and came off plane (with the needle just touching the red, which is the reserve which is supposed to have 20 or 25gals), first one engine shuts off, then the other and now I'm adrift... Toss the anchor! Luckily, Sea Tow was minutes away and came to the rescue.

What I learned...if you are low on fuel, don't stop until you get there! It reads alot different at the running angle than it does at idle! At least now I know exactly what my limitations are!

Hmmm... mine has never been that off. I had it out yesterday, into the red, and filled up at Haulover. Conditions were amazing yesterday btw!

Pickups are usually short so you don't pick up any sediment either.

...plus if you reset the SC5000 when you top off you will know exactly how many gallons were burned. I can predict to the 1/4 gallon when the nozzle will be clicking off at the next fill-up.

wtf? look guys i have been having the same issue with my little tank . I own a 223 ls with a 80 g tank and sometimes it reads 1/2 and some times the ***** reads 3/4 . depending on how much beer goggles have to do with it but . sure as a wiz fart i am certain that it cant be that off.

I have a F223LS as well, but I did two things to get a better idea of how much fuel I have left. 1st, I installed a Hardin Marine Hi-Perf sender (no-float design). Then I installed a fuel flow sensor/gage (NavMan 2100) to accurately measure how much fuel I have burned. The combination of these items will almost guarantee that I will not run out of fuel. The F223LS does not have a "reserve" of 20-30 gallons when the gage reads 1/4. Depending on your float angle, the amount of fuel left before the engine pickup is starved will be about 10-15 gallons...Remember, the fuel pickup is not on the bottom of the tank. It is about 1-2" above the bottom.

IMHO..The NavMan fuel flow meter is certainly the best way to go.