How does Yamaha math work? 210 fsh fuel

[ShireRider]

I have been running close to shore. I see my local marina switched to VP fuel so I ran my tank down.

The gauge said 24% this is on the water.

I just pumped 46.8 gallons into a 50 gallon tank.

Is the gauge that far off? I’ve put in 25+ gallons at 78%.

What am I missing?

 

[Coult45]

@210 FSH will give you a better answer than me to help you maintain a pretty accurate estimate of your remaining fuel. I'll just reinforce your opinion that the gauge is not to be trusted...my gauge has only shown a percent remaining number in the 90's once in three years. It shows 100% for a while, then drops straight to 87%. It then wanders slowly and inconsistently down until I fill it back up. My trips don't run me that low, and I carry gas cans to my dock a few times a week, so gauge accuracy just hasn't been important enough for me to worry about it.

But you're right, it's not to be trusted as your only source of truth. I'm guessing the angle on the trailer vs the angle on the water makes a significant difference too.