value question

I have two lawn boy mowers one is a model 10318 4 stroke silver series and the other is a model 10552 2 stroke gold pro. They are both in excellent condition and mow great. the question is how do I find out what the value of the two are. I cannot find anything to suggest what I would list one for if I wanted to sell it. I am considering selling the 10318 but really do not know what the right price would be. can anyone on here give me an idea of fair market value for it?

thank you in advance for your help