Tsunami prompted Yamaha Generator Test. Low voltage output Ef-12000DE

Being in Hawaii I got out my Yamaha EF12000DE Generator on Saturday to get prepared. Started right up, motor hummed along at seemingly adequate rates. Upon testing the 120v outputs, I could only get voltages around 85. The generator was last run more than a year ago and it seemed to run well at that time. Any thoughts? Anything may help.

I hooked up a shop vac to the outlets and it ran, but slowly. Luckily the tsunami hit, but the waves were small and we only experienced a few surges of in and outgoing water. No need for my generator. None the less, I want my generator ready when we need it. I read that my armature might be rusty from storage, but I'm not too familiar with getting to the insides of a generator. Thanks in advance from Hawaii.

You may want to give this thread a read. It wasn't a Honda Generator but several things were covered.

Do you have the owner's manual and a schematic of your unit?

Ron