summerizing our boat

Mike took the boat to Happy Boaters here in Cartersville to get it ready for summer. The owner, Dave, quoted $175 to get it ready for summer.  As he was asking us questions, I got a bad feeling. My gut was telling me he was trying to find out how much we knew about boats so he could BS us and get more money out of us. I told Mike my feelings when we got home. Sure enough, Dave called us to say the engine was shot, but hey, he could put in another for $7,000 or "take it off our hands" for $3,600 and put us in a $15,000 boat. I disagreed and told him I wanted a second opinion. He then got haughty and told me that would be a waste of money. I instructed not to do any more work and we would pick the boat up. They had dismantled the outboard and other parts when we picked the boat up. He still wanted the $175, but did cut it down to $125. We took the boat home. A couple of Mike's friends started working on it and, guess what, the engine started right up. There was a kill switch to be turned on, apparently. We approached Dave again, showed him the video of the boat starting, and wanted our money back. He said he had to talk to the guy working on it. We complied and one of our friends went with us to talk to him. Dave had to talk to him alone. When he was done, Dave came out and said he wasn't going to give our money back because we "paid him for an opinion." I said, no, we paid you to get it ready for summer. You didn't do that. He said he didn't know what miracle happened to get the engine running, but he stood by his opinion the engine was blown. He also claimed he didn't want us to spend any money on the boat and advised as such. I called him on his BS and he called me a bully. My advice, do not take your boat to this guy.