Weak GPS notice when sending messages

Probably because there were no satellites within 45 degrees of your device. If the satellites are close to the horizon, they are too far away. You can go to ConnectIQ and download IridiumWhere (IW) app. IW will allow you to see where the satellites are, much the same way you can view GPS satellites. I have watched as a satellite moves into the 45 degree circle, my message will send, when it wouldn't previously.

I think he gets poor gps message

I would say look onto the satellite page what the current status of the gps is. And yes, when you set your device to save lot of power, like exped mode, then it may need some extra time to make a fix to be able to enter the position into the message

This message has to do with GPS fix, not the Iridium constellation.

This comment has to do with sending messages. I realize the original commenter used "gps" in the comment, but I think that is an error, since GPS is not used for sending messages.

sure is GPS used when sending messages

if you set it up so position should be included with messages, I think most people will have it this way, then you need a fix before the msg can be sent. This is where such warnings come up.

The original commenter stated he sent the message and the location was accurate. That suggested to me that it wasn't actually a GPS problem. It would be odd to have weak GPS reception on the open water. But maybe that's what actually happened.

The error note  received every time sending a message is quoted below.  This with all strong satellite reception. Clear view of sky and accurate position shown on map.   A friend’s 66i is receiving the same error.   If I choose send “anyway” the message is sent with the correct position included.   Any ideas?

” Poor GPS strength.  This may cause inaccurate or missing message locations.  Orient the device so it has a clear view of the sky”        Choices    send Anyway   Or Wait for GPS

Open a support ticket. Might be a f/w bug or a problem with your unit. I did not look, but the article mentioned above probably mentions the possibility of a stale EPO file. Coupled with the fact that the 66i conserves power by attempting to acquire only when necessary (for example, to send a message), this could be causing the warning. 

Sounds like a software bug. Obviously you can't actually have strong satellite reception and poor reception at the same time. You can contact Garmin Support, but don't expect expediency. At least it seems to be working okay otherwise. If you get the error note again, check the Satellite page to see if that gives you any insight. I don't expect it will, just grasping at straws.