Thanks for all the input. I went ahead and offered him $250 and he thinks I'm being unfair

. I mean how am I at fault. It ran good when I pulled it and beyond that I didn't know.
Tell him that you KNOW he was trying to profit off you on another motor. The $250.00 is all you will give him. You only are willing to do this for seven days after that it is off the table. If he says ok when he comes for money or says send me a check you write "by cashing this check you release all future claims on (insert your name).
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If he wants cash or wants to come get it You have him sign a release.
Basically
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I (his name) do release (your name) from any and all future claims resulting from the sell of one used (describe motor type) on (insert date of sell). The said motor being sold on (insert date) and was picked up on (insert date). On (insert date) buyer claimed motor was defective.
You will need a witness like a neighbor.
*end of release
Then this would be how your records should read for future reference. I hope you kept those emails and voice mails.
AFFIDAVIT
On (insert date) (buyers name) contacted me regarding a (motor type) that I had for sale on (how you were selling it). I informed him the condition as I knew it as described to me (then just what you told him). The buyer then paid me (insert amount) via (how you got the money) on (insert date).
On (insert date) the buyer picked up the motor from me. At which time he made no attempt to check motor or inspect it. On (insert date) the buyer contacted me stating the motor was no good. (Write about the contact and mention what he wanted)
Buyer wanted to purchase another motor from (other guys name) for (insert amount). I contacted (name of guy with other motor) and was informed he was selling the motor to (your buyers name) for the amount of (insert amount). The buyer (insert his name) attempted to defraud me by requesting more money than was required.
On (insert date) I offered the buyer $250 toward the motor from (other guys name) with a time limit of seven days. The buyer declined the offer.
What he is trying to do would be Attempted theft by Deception. Money is property.
2913.02 Theft.
(A) No person, with purpose to deprive the owner of property or services, shall knowingly obtain or exert control over either the property or services in any of the following ways:
(3) By deception;
Here is what the ORC are definitions:
(A) “Deception” means knowingly deceiving another or causing another to be deceived by any false or misleading representation, by withholding information, by preventing another from acquiring information, or by any other conduct, act, or omission that creates, confirms, or perpetuates a false impression in another, including a false impression as to law, value, state of mind, or other objective or subjective fact.
(B) “Defraud” means to knowingly obtain, by deception, some benefit for oneself or another, or to knowingly cause, by deception, some detriment to another.