Good to see someone actually taking the time to do baseline testing.
I am not surprised & I have said before that this was my experience dynoing 2 of my own merc engines.
Then I was attacked by a legion people that havent ever seen a dyno that I was full of it and "anti merc" & that they all deliver "way more" HP than claimed because "all Merc # 's are at the prop". (BS)
I love merc, and would do the same thing if I sold engines like this en mass and had to warranty them from newbys.