1994 Yamaha 225 Saltwater

I just bought this engine and am a little curious of the "normal" sounds mad by the big V6's. I have not owned one before. I had it checked out (compression, foot, etc..) before I bought it. With the cover off, idling it almost has a clickey-clack or a light almost diesel like sound on the exhaust (back) of the engine block. Is this typical of this engine- it has 400 hours. I don't remember my smaller Merc 150 doing this. The engine starts and runs great, however it does smoke a decent amount after a good run and then fishing a little while.

Thanks

[boats.net]

Normally you don't hear any noise from the engine.