Generator problems that I run across most often are due to: 1 long periods of not running. 2 Corrosion
due to Generators getting wet 3 Bridge Rectifier failures (Westerbeke). 4. Gasoline generators are prone to "gumming up" the carburetor due to the new "Government (read ethanol) fuel
One example of a major generator failure occured to me on a yacht that was kept in "mothballs" in Florida
for a few years......The generator ran fine for about 20 hours.
Then, at an anchorage in Nantucket
, WHAM smoke.....lotsa smoke....sparks.....
The windings shorted out.......come to find out, that the shellac that seals
the windings is great food
for some bacteria/bugs........it only took one bare wire to cause the whole mess to blow......By running the generator frequently and getting it up to heat kills those varmints.