ltkhbl wrote:
I have two 120 watt panels on my catamaran. They now only put out 6 volts.
What series of steps would you suggest to find the problem? They have worked
well for the past five years.

Test each panel individually. From the Shell Solar panel instruction
book:

"Check the voltage of individual isolated modules . . . A reading 1/2
of the specified voltage indicates a short circuit of a bypass diode.
.. . [A good diode] will have resistance in one direction and an open
circuit in the reverse direction. Continuity in both directions
indicates a short circuit of the diode."