Dear Graf, thanks to you the problem is now solved
The engines were indeed recharging even though the CE menu didn't show it, and simply asking for standard propulsion fixed the thing immediately. The boat is moving like a wolf
that got it's tail stepped on now 
Yeah, I'm glad things are finally rolling again - we're a happy bunch now, every station fully manned with alert men, 50 hands all counted and everyone itching to sink some more Engländer shipping of course!
