The boy often hanging out here is interested in statues .为什么

The boy often hanging out here is interested in statues.
这句话可以完整地表述为：The boy who is often hanging out here is interested in statues.
现在分词在这里表示“状态的持续”,是BOY的后置定语.
hung out 是hang out的过去式,上面句子的主干是The boy is interested in statues.系动词is是现在时态,当然不能用过去式了.

那个经常探身出来的南海对形势很感兴趣。
hang out：用ing形势做定语。