2007 Mercury 250 pro xs 2 stroke

by Andrew Cobb
(Cantonment, Fl)

I just purchased the boat from my dad so I know it's been taken care of but anyways when he bought it the powerhead was replaced with a brand new 2013 power head and it has 56 hours on it as of today. My issue or concern is when coming off plane sometimes there is one solid knock out pop almost like a knock from a diesel motor on a cold morning but I've only noticed it coming off off plane. And it doesn't all ways do it either. Besides that it runs great no other problems or concerns at all. I did just remove the lower unit the day before I took it out but I don't think that could have caused anything... Thanks for any help