Which is what the rudder's for. It'd just be hard to make a turn to the side that the working prop's on.
With an unfortunate name,
Shafting a Ship is a good article about how many shafts a ship should have.
Quote:
The first consideration is weight economy. The propeller, shaft and gearing all represent dead weight that is duplicated with multi-shaft arrangements. In addition, the curve of engine output power as compared to size and weight is not linear; two smaller engines together weigh substantially more than a single larger unit of the same output. It may, therefore, seem that an ideal arrangement will involve keeping such duplication, that is the number of shafts, down to a bare minimum. Provided the total power in question is below the maximum that can be absorbed by a single propeller, then a single shaft arrangement would seem to be the most efficient. If the installed power is greater than the maximum that can be absorbed by a propeller, then the most efficient arrangement would be that involving the fewest number of shafts; in most cases two. Another way of saying this is that the most efficient design for shafting is to load the propellers as highly (that is, to put as much power through) as possible.
For merchant ships this is indeed the case. Merchant ships are designed for economy of construction and use, not for the most efficient use of high power settings. In their case, the economic advantages of a single shaft outweigh any disadvantages from the layout.
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The article then goes on to show that that's not the case for warships due to needing redundant propulsion providers, the ability to provide steering via the props, etc.