Right, I have the facts now... it was 4 engines and 2 bikes. Engines ranged 50-115 I think.
They removed 3 of the 4 bolts and then used the whole engine to lever against the locking bolt. Presumably it must have broken the bolt through the engine bracket.
They carried the engines about 60 yards down the compound, over a ditch, through a barbed wire fence and into a van waiting in the field behind.
Thankfully the damage to the transom only looks superficial, some chips to the gelcoat, a gouge out of the plastic pad on the outside, and the locking bolt has been pulled into the GRP slightly on the inside.