As a boat watcher, my wife and I often visit the locks up in the Soo. All of the boats we see go through all have HF antennas on them. From a boat watchers site I visit, I found this:
HF on the lakes
HF used by various shore stations around the lakes. With VHF and cellular phones these frequencies end up used most often to provide weather reports and notice to mariners broadcasts. Every great once-in-a-while you will hear a ship to shore phone call on them. All listed are upper side band unless otherwise noted.
Freq/ Station
2514.0 VCC Quebec CG Radio
2550.0 WLC Rogers City MI
2598.0 Canadian Coast Guard
2582.0 WLC and various Canadian CG
4369.0 WLC wx and some phone
4381.0 WLC
4408.0 WLC
4143.5 Upper Lakes Shipping (Canada)
6218.5 Upper Lakes Shipping (Canada)
5692.0 US Coast Guard - Traverse City and Detriot Air Stations
Boat watching With a VHF Scanner
The real truth to HF on the great lakes is for us to monitor these frequencies.
Over the years, I've heard special event stations on the ham frequencies (usually 20 and 40 meters) from active freighters, usually docked, staffed by hams from a local ham club. One special event station I've heard several times from lake freighters and tugs is out of Rogers City, MI.
Using the formula to calculate distance to the horizon, a VHF antenna mounted at a 100 feet and a Coast Guard Station provides a line of site of just over 12 miles. Say the boat's antenna is mounted at 40 feet, that give antenna to antenna line of site of 23 miles. That just isn't enough distance to provide constant VHF communications on the Great Lakes. HF communications still has a value.