For people who are playing an EU4 save with the Navigable Great Lakes mod, and want to continue the campaign in Vic3, here's how to do so (without crashes):

1. Load the .eu4 save file that's saved with this mod that you wish to convert.
2. Delete all the ships in the great lakes provinces. This prevented CTD in step 5 for me.
3. Save the game.
4. Load the save file from step 3, but this time with this mod turned off
5. Make EU4 run for 2 months. This prevented country misplacement in step 8 for me.
6. Save the game.
7. Convert the save from step 6.
8. Now you can play the properly converted save in Vic 3.