Fuel gauge increases to 100% at throttle

[schaNYC]

Noticed that whenever I’m at throttle, my gauge increases often time all the way to 100% and when I go back to neutral, settles down to true reading. Is this normal, any ideas?

[jkallen21]

Fuel level is based on a magnet sliding up and down an aluminum rod. The resistance is measured based on how far the distance is from the magnet to the metal above it. They can wear out - the defect seems to be electrical rather than mechanical. You'd need to replace the fuel “sender” or “sending unit” - basically the entire rod mechanism with the electrical piece attached (full disclosure: I'm not exactly sure how this part is sold and what comes with it for every boat). The fact that it's changing means that the change in resistance is being seen, it's just measuring it wrong.

[functionoverfashion]

What's the true reading when it's going up to full? If the sender is toward the rear of the tank, it would naturally go up when the boat is at an angle while on plane. If it's going from 3/4 to full that might be normal. If it's going from 1/4 to full, I'd say it's a bad sender yeah.

[srock]

You may be on to something. My gauge only seems to head one direction. As stated, it's the movement of fuel in the tank toward the sender thus the true reading at idle.

[bturner]

Or you could possible have a ground/voltage issue (I know that rarely happens in a boat, right? Nope, happens all the time). Does it do the same thing if you rev the engine with the neutral safety engaged? If so you've eliminated the mechanical float moving as the issue and thus on to grounding and power. If not then I would agree the the above. Where I tend not to follow the movement logic is these are not hulls that should stand on end when running so the level in the tank, while it might move some shouldn't make the gauge go to full, at least none of my inboards or vDrives have. But then again you never know.

[jkallen21]

I was out this weekend and tried to take notice of this. My idle reading was around 1/2 full (or half empty if you’re a pessimist). It would go to almost full when accelerating.