caulking when replacing exterior screws on my rv

What are the stainless screws screwing into? If they are going into another metal, you will get corrosion and then have a real problem. Stainless screws aren't the answer to everything. A product like Tef Gel should be used

Silicone is a great sealant when held in compression. Unfortunately, when it sits outside in the weather, it will deteriorate. I'd use one of the Geocel products because I've had good results. Most of those are polymer based, of which urethane is one.

I fill the hose with a good white silicone and put the screw in and make sure the sealer bulges out around the head to form the seal.

Never a problem in years.

i would use white polyurethane
several brands 3M
etc..