I did a google search for "Four Winns Instrument Panel Repair" and this is about all I am coming up with so far. If you have the gage cluster style installed and it is determined to be the problem, you might try these guys in Huntsville, Alabama. It looks like they might be able to repair your instrument cluster assembly, but there may be some down time.
http://www.cdielectronics.com/dash-panel/This website also has a troubleshooting guide that you may be able to use to verify whether the gage cluster is good or bad.
Another option might be:
http://www.nsifleet.com/service-and-repair.htmlElectrical troubleshooting can be challenging when component specifications are not available. An all to common problem in boats is a bad ground circuit. You might try a temporary jumper wire from the negative battery terminal to the negative terminal under the dash to see if that helps.
The panel on my old '95 190 Horizon had a bad tach maybe 15 years ago. At that time the assembly was reworked in Mexico on an exchange basis. it was around $250 or so. I saw a price from about 7 years ago for $250, and at that time Four Winns apparently also had a modification kit that included all individual gages in a replacement panel that was prewired to plug in to existing wiring in the boat for around $500. A little more expensive........
The gage unit on mine was easy to remove. As you are sitting in the drivers seat, there is a phillips self tapping screw in the top center near the aft edge of the unit in a finger slot. A stubby or fairly short phillips screwdriver should work. Pull the top of the cluster aft and remove it. You may be able to disconnect all connections while you are sitting in the drivers seat. Hope this helps.