It may not have one.
On my 1988 O’Day 322, there is a dial of sorts mounted on the top of the tank…but almost impossible to read.
it looks like this…
it turns out that there is a fuel level sensor under the dial, and the dial can transmit a signal to a standard fuel gauge!
so, I purchased a new fuel gauge, mounted it and ran a wire to it from the dial, and viola! I can see my fuel level.
So, the first thing I would do, is find the fuel tank, get access to the top, and see if there are any fittings that could be a fuel sender. If you find something that wires attached, trace them to find the gauge. if no wires, but you see something like my photo, you may have the sensor in the tank, and just need to purchase a gauge and hook it up.
If you search the SBO site, I had a thread going about the fuel sender…and someone had the make Identified. there are 2 different resistance settings, so you do need to know which one your sender uses to match up the gauge.
Greg