"Not very. They are a referen
"Not very. They are a reference but I wouldn't live or die by them. Depending on how much fuel is in the boat, even the movement of someone walking will cause the fuel to slosh around in the tank causing the float to fluctuates. Your tanks are almost 5' long and carry 142 gallons of fuel, that's a lot of room for sloshing.
Keep in mind also, which tank your genset is running off of. You have a selector valve to switch tanks for the genset. This is useful as it keeps the tanks even and helps keep the boat level.
If your boat is new enough to have the Murphy gages in it, they have a fuel usage mode which tracks usage. That will give you an accurate indication as to fuel used by the engines. They should be very close to the same.
Rick"