Engines stopping on ships

Hi all,
i normally lurk in the SH3 forums, but i'm trying to do a mod for the aircraft carriers in SH3, and can't get round a problem i'm encountering, so i'm hoping one of the SH4 modders may be able to help.
When the boats in SH3 are attacked by torpedo, engines that appear to be well beyond the blast radius of the torpedo, stop, but i can find no logical reason in the settings for the ships, or the torpedoes, that would cause them to do so.

It doesn't seem to matter what kind of ship it is, it happens even with the most heavily armoured ships, the battleships.
I've tried all sorts of zone configurations, doubling the hitpoints for the ships to 2000, raising the hitpoint tolerance of the engine zones, minimising the number of zones in the area etc.

Nothing works to stop the boats coasting to a halt.

Has anyone encountered the "dead in the water" syndrome with the ships in SH4 when the engine bay is hit by torpedoes, and has anyone found the reason for it?