Cigatoo
Guru
Yeah, sorry, I wasn't specific. Idling at about 800. Had a Cat tech there, he didn't seem concerned, I asked, but my experience with diesels was always that black smoke was a bad sign.
When you put the throttles on the pins you are introducing lots of fuel. It may take a second or two for the turbos to spool up and supply the necessary amounts of air.
I am betting that with all of that HP that boat has wheels with a lot of pitch. So even at 800 RPM it will move right along. When necessary you may want to run one engine in neutral to keep the speeds down.