Can I sell this boat?

My husbands cousin left a small flat water boat in our garage. He said he got it from a friend of his some years ago. Any how, he has moved away and since he owes us cash, we asked him if its ok to sell it. He said yes. I noticed a tag on it that says US coast guard and it says the capacity is 450 lbs or 3 people maximum.
I know nothing of boats. Is this just a tag that comes on boats from the coast guard?
Does the boat have to be registered?
Its a small fiberglass fishing boat with no motor. Does anyone know how much it would go for. It has no cracks or holes, except for one hole on top that won’t affect its sailing. Just not pretty is all.
I really don’t care about making money and really just want to get rid of it but I don’t want to get in trouble for trying to get rid of it.
I don’t think his cousin ever registered it. He’s not the type to go though those technical problems.