2nd home ...
Well, you can probably claim it as a second home and the IRS may not track you down (unless you joined the TEA Party

) but I think you can't technically call it a 2nd home if you don't follow the appropriate rules. How would you call a Catalina 25 a 2nd home? The deduction from the interest on a small loan like that isn't really going to be meaningful anyway.
But why the reluctance? I don't know how you define a "big" bank, but you can get a HELOC from a small bank, too. You can go to the place where you have your mortgage so you can deal with the same people. I have the mortgage and HELOC with one regional bank and they are fine. I initially used a very small amount of the balance for home improvement and it was such a relief. There is no need to load up credit cards and pay 12-18% interest and worry about bumping up against the limit. I was able to do what I wanted at home and now have a large balance that I can access for any purpose. For me it has provided total relief from any worry about being able to access money if I need it.
If you don't have a mortgage, then better still, you have equity to access. I agree with people who don't want to offer their home as collateral if they are afraid they can't pay the bills, but if your home is already collateral then what difference does it make?
Hell, the interest rates are so ridiculously low (I have 3.25% for a 15 year fixed rate mortgage and 2.5% adjustable for HELOC) that the actual interest is so low that it barely even serves as a tax deduction.
The freedom to do with the money as you wish, and the freedom of not having the money tied to the boat is such an advantage. Interest rates are sooo low now, it is a good time to borrow on home equity.