[hiccup]

Agree, reach out to Tiara, they may have a p/n and source.

If that's no luck, to help you search, it is a 4 position 3 pole rotary selector switch, although based on your picture, your boat is only using 2 of the positions, so you could get away with a 2 position/3 pole selector switch. Let us know what you find out.

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I also will give you some details on how the switch should work so you can test it with a meter (maybe you already understand this but it may be good for the next person).

Based on your picture, we'll number the terminals 1-15 starting at the top left and working CCW; so the terminals along the left edge, starting at the top are 1, 2, 3, 4 , 5 and the terminals along the bottom left to right are 6, 7, 8, 9, 10 and the terminals along the right edge from bottom to top are 11, 12, 13, 14, 15.

Here is how the switch should operate:
Position 1: 1 connected to 2; 6 connected to 7; 11 connected to 12
Position 2: 1 connected to 3, 6 connected to 8; 11 connected to 13
Position 3: 1 connected to 4, 6 connected to 9; 11 connected to 14
Position 4: 1 connected to 5, 6 connected to 10; 11 connected to 15

Also, because you're only using 2 of the 4 positions, I wonder if it is possible that your switch (which will only send signals to the meters in positions 1 & 2) is position 3 or 4 (perhaps the knob is on wrong).

Just food for thought!