If you have a Yanmar engine and have been reading the manual, I´m sure you know that the elbow (Riser) on the exhaust of the engine should be cleaned every 250 hours or once/year.
I got this picture from a friend with a Hallberg-Rassy 34. As you can see the elbow is plugged to 98 %. Only a small hole left.
The exhaust elbow is living a tough life, and is one of those parts that will have to be replaced on most engines. The exhaust elbow is the mixing point of very hot exhaust fumes and salt water. A very hot and corrosive environment with carbon deposits. (Another reason you should do the Italian tuning)
Volvo Penta does not mentioned anything about inspection in their manuals. Nevertheless, I recommend that you include a check of the elbow independent of the engine manufacturer.