HELP! where is ship blast controlled?

the other day i was shelling a small coastal merchant from about 100 meters when it exploded, i think it was an ammunition ship. The blast destroyed my boat . So today i was shelling a ship and being careful to be at least 200 meters away when it blew up and killed all my men on deck - it must have blown my AA gunner into bits cause i could not even move the body into the front torpedo room with the others who died. my sub sustained an instant 40% damage and listed to starbord all the way home.

so my question, one of you mod gods must have seen the specs somewhere in the SH3 data that spells out just what the blast radius is for exploding ammunition ships! what's left of my crew could sure use that info.