I realized that he really didn't give us all the information. Specifically, he doesn't say from what direction the m/v was approaching or what direction it turned. For some reason, I envisioned the m/v overtaking the s/v from astern, but upon rereading Dan Y's post, I see that he never said that.

Karl, I don't pretend to be an expert on the COLREGS, though I should probably become so since I operate a s/v. My philosophy has always been to make course changes way early in order to keep clear of other vessels. At night, I generally try to keep at least a 1/2 mile of separation between my boat and any m/v's out there. In the case I related, before I made my initial course change, the radar showed that we were going to pass the fishing boat approaching us from the front stb to stb with a separation of 200-300 yds. I chose to turn away from him (to port) to increase the separation. According to COLREGS, if I was uncomfortable with the amount of separation (as I was since fishing boats are notorious for radical course changes), should I have turned to stb instead, crossing in front of him and trying to pass him port to port?