Looking at a marine 3.5Kw generator the rating is 230v? I'm a little stumped

It probably means that you can receive both 110 V from a plug, and 220V volts from another plug in receptacle.
Don,t think I,ve ever seen a small generator that only produces 220V, which would be kinda useless for most applications.

Can you post the make and model of what you are looking at, or a link to it ?

Thank you for replying

Mastervolt Whisper 3.5 230v one suggestion I got was it may be a European model??? They use 230v?

After spending some time searching on the net, this one has got me stumped.
Hopefully others can give you some good advice about this unit, and if it will work for your intended use.

Doing a little research: part# 50900555 120/240volt 60hz. This would be the unit you would use in the US. Model 50900500 230volt 50hz would be the model for Europe. It can only run 230volts.