Must have been a rainy day
Hi There,Well now 75% moisture content inside and out eh? Could it have been raining in Chicago that day?You live as I once did in a very humid climate, so it really is no real surprise to find maybe the humidity at 75%. If the boat is in the water for the survey as you really didn't state in or out, I would assume that the moisture content should be right around 100%If you would like to keep the moisture content inside to a minimum then I would be looking to install a fan powered by solar energy to exhaust the moisture from the humidity buildup there in the midwest. My home state of Michigan is no different.You might also want to consider a simple 110 volt dehumidifier as well as the fan . I believe you can find these items at your local marine hardware or West Marine catalog, or even Coastal Marine catalog.Hope this helps

Dave LaPere