Yea the engines don't work submerged anymore, they can probably be replaced with steam now.

In the two years since this has been uploaded nick has killed fuel engines by making them explode constantly, and introduced steam engines that are basically better than every other engine in the entire game.

This is a very good early and mid game sub but the only problem is the cylinders overheat when you go to fast its a good way to limit its speed but not very helpful in a situation were you need to move the sub in battle