Good morning Larry,
I'm Doug, and I'm very sorry to hear of your situation. My goal is to provide you with excellent service today.
If your written contract says that you will accept no less than $12,000 for your boat, and you orally agreed to accept $10,000 cash if they sold it for $12,200, then you may insist that they pay you at a minimum the $10,000 that you verbally agreed to.
You will also want to look at the original consignment contract that you signed and see if there is a clause requiring any modification of the agreement to be in writing. If that is in the written contract, then technically you can refuse to even accept the $10,000 and demand the full $12,000.
They have no legal basis to keep any more money than you agreed to, and the worst case scenario leaves you with $10,000 and if the written contract does require modifications to be in writing---then you have negotiating leverage and could legally hold out for the full $12,000.
You may reply back to me using the Reply link and I will be happy to continue to assist you until I am able to address your concerns, to your satisfaction.
I hope that I have been able to fully answer your question. As I am not an employee of JustAnswer, please be so kind as to rate my service to you. That is the only way I am compensated for assisting you. Thank you in advance.
I wish you and yours the best in 2016,