One thing that I have learned with eBay is that you have to play the game. Setting a reasonable reserve kills the sale right up front. For example, I sold a really pretty little ultralight that I had aquired. I set a reasonable reserve of $6,000 and started the bidding at $5,000. Nothing happened. I relisted it. Gritting my teeth I set no reserve and started the bidding at $100. The plane ultimately sold for $8,400. You need to get a bidding frenzy going.
I also sold a propeller, seats and other things. Low starting bids and no reserves got me more then what I expected originally.
But, admittedly, it sure is hard on the nerves. For someday it is not going to work!

After selling 72G a little less then a year ago, I have doubts about your $16,000 reserve. Unfortunately for you, like Carl points out, there are lots of cheap 150's out there. That high time engine is going to hurt. But, there is possibly a silver lining maybe? How long has it been since it has be top ended? If you have a fairly new top end, you may want to advertise that for it would help considerably.
Good luck!