I wonder how many of these Iranian flagged ships being disabled or seized have a magic pipe installed by their CHENG? Or, is that just a western / Marpol73/78 thing and they don’t care about concealment?
Well if they take a round from a 5"/54 through the engine room, it’s easy enough to just pump off all their sludge/wash/oily waste and say “oh, the tank was damaged… it’s a leak” 
I was about to say the same thing. Calling a ship to tell them to evacuate the engine room so you can blowup the engine with a cannon is going to cause oil to get into the water. My company has a hard time scheduling ABS & USCG Marine Safety Officers for annual inspections. I’m on first name basis with a few USCG inspectors & I don’t think any of them will go to the Persian Gulf to inspect captured tankers. The US Government can just say they all have magic pipes, meth labs & puppy mills on board & it wouldn’t make a difference one way or another. We’re blowing their shit up & taking what we want regardless.
That’s right! 
gotta take the opportunities as they come!