First of all a general note. 5200 is a great adhesive but a so-so sealant. It doesn't flex like a lot of others. The PO of our boat was a 5200-ophile. Used if for everything. Grrr. I have used it where I need really good adhesion with good results.

I think you would be good. 190° is very hot. We use 60°C (140°F) as a safety limit for our industrial equipment. We have done some informal tests and found that 140°F is the temperature you can touch, react with "whoa, that's hot!" and pull away without a burn. Any higher and you have a burn. If in doubt get a low-cost infrared thermometer and check your tank during operation. For the IR thermometer to work you will need to put a spot of paint to get an accurate reading. Shiny surfaces do not read true.