On that year model, I'd think that corrosion has had it's say and the line inside the meter is clogged. If you have an air compressor or can blow hard, you can disconnect the tubing at the rear of the instrument and at the pickup source and see if you can blow through it. If so, meter is in need of replacing. May have them on this site...check at the top of the page under Boat parts and accessories. Otherwise pickup is clogged or hose is clogged.
