Hi Jared and welcome to the forum.
Rent to buy is a tricky deal with boats. First, they are very portable so a seller may be reluctant to rent something to a stranger that could then easily take the boat hundreds or thousands of miles away, even to a different country, without paying.
Second, it isn't difficult to damage or even sink a boat so again, a seller might hesitate to rent a boat when something could happen to it making it worth less or worthless.
That being said, someone desperate to sell a boat in a soft market might consider your offer but will probably ask for references
or even collateral.
One suggestion, I guess you haven't read this forum much but it is international with members literally all over the world. It would help you a lot to get a possible reply if you would mention at the very least what country you're located in. Better if you could be even more specific.
If you're in Maine
a boat for sale
won't do you much good and yest, we have a lot of members in Australia