How to Perform a Yacht Electrical Balance

Google Archimedes' Principle.

If you want to weigh the yacht, lift it out of the water with whatever what can lift it. If you put a weighing cell between each of the lifting points and add the results, that is your weight.

If this is electrical enough, that is one way.

Some devices use hydraulic motors and measure the pressure of the oil, needed to lift- resp. hold, the boat out of the water.

A good manometer, will tell you the weight too.

With pressure - to- voltage or current transducers, in the hydro circuit, you might have a second way of doing it. Most electrical I can think of is measuring the current of your "electric" lifting (winches) motors en make a correlation to the weight. You can use any calculator software that can add.