I have no idea what a "Sales Tax Credit Trade-In Program" is, but sales tax for large items (such as the boat) can be added to the sale tax deduction if you are itemizing deductions on Schedule A. 

However, if you live in a state with income tax, it is quite possible that the itemized state income tax deduction would be larger than the sales tax deduction, in which case the sales tax deduction would not reduce taxes.