Between January and April, just before fishing season opens up here in the NE. Here's why:
Boat shows - many of them are in the winter mos. A guy goes out and has the same craze he did when he got married, only this time it's a boat. Whoops, he already has one. Now he has two. He has got to sell, and especially now, boats aren't moving real fast. Other factors included in the winter and early spring sales are payment of taxes, and the need for cash for some people.
The fall is OK but prices are higher then than in the late spring when the seller is up against a deadline. If a seller puts a boat up for sale in the fall, he's figuring he has 6-7 mos to sell it, and he more than likely won't be highly motivated to move it quickly. But if you can keep your cash in your pocket until March, and find what you really want, you should be able to swing a good deal. BE PATIENT!!! I watched my boat for 4 mos, even visited it a couple times. Then came March, the seller was in a panic. Got the boat for 25% less in March than he wanted in October.