Well, it isn't a correct translation. Google isn't very good at that.

I would translate it with "So weigh carefully before you bond yourself forever".  

The google translation isn't exacly wrong, but neither right. Jules words in english aren't really a tranlation, but have a similar meaning.

A ship in port is safe; but that is not what ships are built for.
Sail out to sea and do new things.
-"Amazing Grace" Hopper

Avatar image of me done by Chidori.