Water pump clarification

[Garry Wills]

This thread interests me, particularly the last comment. My assumption from the reading the rule book is that you only have one repair action a turn and therefore a ship with multiple leak damages will sink fast. I have just had a double-shotted first raking first-rate broadside inflict 4 leak damages on its opponent. So if I have understood the rules properly the unfortunate ship has 4 damage boxes filled on the first move an additional 3 on the second move (one leak repair and one pumped), which on top of the actual damage sunk it. Obviously with only a 6.7% chance of pulling a leak chit, this was an extreme result but it has tested my understanding of the rules. Presumably multiple fires work the same way. Fires and leaks in filling whole damage boxes seem more damaging than cannon fire. Have I understood this correctly?
Thanks Garry