Bondo nails it. If you are going to spend $6k and up, then take your time. $6k is getting into high end for a used boat with a 3.0L. The 3.0L is typically the entry level offering for most boat manufacturers. You can find some great deals in that market as people tend to move up to bigger boats with more horses. You also find a lot of neglect, often just from ignorance of the newbie boat owner or financially limited owner who didn't understand how much it costs to own and maintain a boat.
You will not have trouble in the spring finding nice boats in your price range. Make sure the structure is sound is even more important consideration that whether the motor is perfect. Motors are very easy fix, rotten transom or stringers are the spendy fixes.
Most important of all is defining your boat layout for a fishing rig. Most 3.0L IO boat models are runabouts and not all that useful, overall, as a fishing barge. Access across the rear of the boat is severely limited, especially by the doghouse cover over the motor. Side rail space is restricted by stylish design made to look good. I converted a 3.0L runabout style boat to a fishing boat, and it suits fine for the type of fishing I do. BUT, it would have been a step up in usability if I had chosen an outboard. The biggest PITA is working the back of the boat with downriggers on both sides and a trolling motor needing tending in one corner at the same time. Scrambling around the doghouse to reset the tiller, while trying to get downriggers set to correct depth, is a monkey fight. I have found that my boat is really only a 2 person fishing craft unless one person stays at the helm and keeps the heck out of the way of the two handling rods and nets. It is a joy cruising to and from the fishing grounds at speed. The design keeps the wind down and really comfortable reclining chairs make for a comfortable day for the wife and I. If I did it again, I'd go an outboard in a second. My initial reason for buying the IO was I knew I could work on it. My informed reason for considering them now, is I know I could work on an outboard too. Outboards cost more, but serve the task better, IMHO.