Originally Posted by SeaSkills
Sorry, but that's just sloppy.
If you're ever in a position when you need to make a Mayday call (ie grave and imminent danger), I suggest you should do everything you can to help people rescue you.
It isn't hard. There is plenty of good advice coming out of this thread. If your life is at stake (and the lives of other people who are out in the boat with you) - why wouldn't you want to give them the best chance of survival?
You are getting this backwards. The most important element to summon help by any means possible as the ship is on fire or sinking. (Otherwise it should have been a Pan-pan)
The MMSI is gravy. Nice to add if you can in ideal circumstances but in many cases not likely to add much to the efforts to find and extract you and your passengers. The MMSI is a string of numbers which could with iffy communications be misunderstood as position information. When in doubt Lat/long takes precedence over MMSI.
In this country our own Coast Guard only got universal digital capacity in the past couple years. In many countries it doesn't yet exist on the ground. So emphasizing the MMSI is misplaced IMHO. I would also add that most recreational vessels in this country don't even have call signs either. The requirement to get one for domestic voyages was relaxed many years ago.