Don't be silly
we use steam cleaners to clean tractors - ye'd knacker any carpet, curtain headling or oven if you set a steam cleaner anywhere near them.
Why would you want to induce so much damp into the interior of a boat anyway - you'll be paving the way for a real good crop of mildew as you'd never get the damp moisture content down particularly in headlings or carpets. A steam cleaner is far too harsh an application