Ok, first of all: I did not fight that coastal battery, it surprised me while on time compression until I took 2 or 3 hits, which were enough to bring my engines down. Just to make it clear I was not trying to get involved in a major surface engagement with a sub.
If the diesels suffered unrepairable damage, shouldn't they be marked as destroyed in the repair screen? Instead, they are shown fully repaired.
Maybe I should tell: the thing happened with an S-18, not a fleet boat. As far as I know the S-18 used the propulsion system similar to u-boats.
@ ancient, I'll try it next time this happens, thx