Hang in there OP.

It is probably more than 30 days since the transaction went through and most credit card company would have already transferred funds to the seller. A credit card company can not go and take money out of another person account without authorization by that person. Had the buyer informed the credit card company of a problem with the merchandise in a timely manner, the credit card company could have placed a hold on the funds.

The credit card company may reverse the charges on the condition that the engine is returned to the seller. The money will be returned to the buyer account once confirmation by the seller that the same engine that was shipped has been returned. They will not reverse the charges as long as the engine is in the buyer possession.

eBay have the same policy. If you are dissatisfied with a product from a seller they will refund your money once the item is returned to the seller.

In looking at the photo of the motor your supplier sent you it looks like it came off the bottom of a lake. Plan on pulling the heads. What was the issue with the original motor?

knocking sounds coming from the engine.

There has been no response since the original post by White46.

There has been no mention about what was wrong with other engine even if there was one, no mention of a knocking sound or even if it is available. We don't know if it was shipped, we don't know how adamant seller was it is not his problem.

I've worked with engines that looked worse than this 4.6 inside. Cleaned them up, dropped them in, squirted a little oil in each cylinder, fired them up and not a problem. If I were seller I wouldn't take the engine back yet, regardless of the warranty, not enough information to know if the water has caused a problem.

The sky is cloudy, it has not fallen.

Credit card companies most certainly can recover the funds even after they've been paid to the merchant. As for returning the engine I think that's reasonable as long as it's at the sellers expense.

Having said all this I'm not sure why you're opposed to the buyer even making the attempt to recover his money.

I'm not a mechanic but one thing I do know is water should not ever be inside an engines cylinder. I watched the video and it wasn't just clear water that came out. It was brown...suggesting it had been there for quite some time.

Assuming the water was not a result of something the OP did (or did not do) then it was sold that way and if I were the buyer I would demand a refund. I wouldn't waste my time with it further.

I think OP is not coming back. With 4 pages worth of responses and he isn't participating, I say leave this one alone. It bugs me when people come here with issues and then don't participate in the conversation. I actually find it really rude. If you don't have time to check in for the help YOU requested, than you don't deserve our time or effort. I know that some problems will help others, but this is a semi unique situation and he is way out of his element on the problem. Let's let this one die a natural death

He is definitely in over his head by the sound of it. Me personally I would have torn down the original motor before hitting the buy it now button on the replacement.

I think it's too early to say this. The op only posted late Thursday night so it's only been a little over two days. Two days which the OP may be spending working on his engine(s)