Two things come to mind here. One is "Buyer Beware". I am sure the Bill of Sale states "as is" The other is the Broker is not liable as they are just relaying information they were told by the Seller. Going to court would be a waste of money unless you have something in writing stating the engines were rebuilt. In that case maybe you could after the Seller.

Licensed brokers and used boat dealers have a lot more liability than individuals, and the courts are real familiar with those issues. If this was a "big high dollar broker" as the OP stated, they will be real familiar with their liability and obligations. As-is doesn't by default discharge a broker from liability. Saying "I just said what he Seller told me" doesn't fly when compensation is taken by the broker. He/she still may have liability.

It is one of the biggest, and high dollar is an understatement.

This makes me want to know...who??? and which boat??? LOL...

All in the Buyer's favor. Hopefully this was an oversight and the Seller understands that the two situations (165 hours versus 510) is material and offers to either document the misunderstanding or otherwise make it right.

you can make an hour meter read anything you want it to, not true with a ecm

Bottom end if not always run at 4000 to 5500 should be ok for a season or 2. He owes you everything from the head gaskets and lifters on up. And THAT is payment to you for eating the extra 350 hrs on the blocks, without a lawsuit...

You would be ok with just getting top ends done on 500hr engines that were suppose to have 160hrs on them? I know i wouldn't.

Hour meters mean absolutely nothing. ECU engine hour meters show how many hours there were used. They will not show if an engine has been rebuilt. They could also not be the ECU that came with the engine. IMO they should be taken serious, but they could be miss leading by people looking to take advantage of someone.

This is why I think my next boat I want to buy it knowing engines are trash so I can just go to who I trust and have them built/rebuilt.

Hear this far to often.

Then at least you know what you have!