Was the trailer included in the sale?

Did you see the boat?

How did you make an offer? Phone, fax, email, in person?

Did you speak with the broker?

If you spoke with the broker, and made a reasonable offer, you should have insisted on a response in a timely manner.

If you don't get one, then you should withdraw your offer. You don't want the broker to be using your offer to get better offers from other interested parties. Assuming the boat is still available.