Even if the hull is made of fibreglass, wouldn’t all the metal in the engines emit a magnetic signature?,(reply>), Vessels like this can have electrical magnetic field generators around the engines and other big metal bits to produce an opposite field to the engine itself, so cancelling it out.,(reply>), James Huke <br>O definitely and engines have been. So your correct the only down fall is expense and occasional quality,(reply>), While it's probably not relevant to this, I'm sure a non ferrous engine could be made.fom various alloy's that would make it much more magnetically hard ie harder to magnetise,(reply>), Yes but it’s likely that it would not nearly be powerful enough to attract sea mines.