Is RV (second home) interest deductible (if) its not secured by our home? And we didn't rec a 1098?

The mortgage must be secured by the RV as a second home for the interest to be deductible. 

You can likely deduct the loan interest paid during the tax year on your RV as a second home as long as it meets the following qualifications:

• The loan is secured, which means the lender has some kind of guarantee of payment, usually in the form of property. If a borrower defaults on payments, the lender can seize the property that’s securing the loan. If you’re buying or refinancing a home, the loan is usually secured by the home (which is the RV home in your situation) you’re buying or refinancing.
• The home with the secured loan must have sleeping, cooking, and toilet facilities.
• The debt can’t exceed $750,000.
• You or someone on your tax return must have signed or co-signed the loan.
• If you rented out the home, you must have used the home more than 14 days during the tax year or 10% of the number of days you rented it out, whichever is greater.

Here's how to enter it into TurboTax Online once you have retrieved your information from your lender since you didn't receive a Form 1098 Where do I enter my 1098 mortgage interest statement?

If the RV loan is secured by the RV, you can deduct the interest, even if you did not receive a 1098.

If the RV loan is unsecured or is secured by some other property, even including your main home, the interest is not a deductible.

If the RV was financed by the mortgage on your main home, it counts as equity debt and you can’t deduct that portion of the interest from your primary mortgage either.