Not quite.
You bought the boat, "as is", never bothered to have it inspected prior to the sale, and then your husband did work on it. AND you turned down the warranty!
Sorry, but there isn't a court in the land going to rule in your favor.
And no reputable "real marine mechanic" is going to stake his reputation in that matter.
But you know what? Even if he DID, it's STILL nobody else's fault but yours.
My husband didn't work on it!!! He only added a a second (backup) battery and perko switch. As for inspection.. the boat was on blocks on the entire time.
Unfortunately, we went on his word that it was a turn key boat. We did hear the engine running. it sounded great... according to my husband.. ran very quiet.
The only thing the business owner offered us was to take the maiden voyage with us, which my husband unfortunately declined. We live about 15 miles from the shoreline so it would have been a process to test drive this. We were taken by this business owner.