You could be running out of hull.
Every hull will only run so fast no matter if you put 2000 h.p. in it. I forgot what the technical term for it is called.

the guy I bought my 25 from had a 700hp 572, he said it would do 84 with a little more throttle to go but didnt want to turn the bravo over rpm . not sure if that was a GPS speed or not, my speedo says 78-80 when my gps is only on 73. something

addiction your boat did 84 on the gps and had more if you wanted to push it past 5300 rpm, that boat belonged to a really good friend of mine, and i'm hating myself for not buying it.

HA HA!! I love it. Tell Rob I said Hi It was rpms now that you mension it.

Oil temp sounds a little hi to me. Jeff had some good info there. Mayb a trashed oil pump? U need to figure out what is going on...You may have some predetonation going on too and will soon have a hole in a piston. If you had something happen in the outdrive that was severe enough to kill the engine while underway, trust me, it would be in pieces.

Try a compression check/leakdown test while you are at it.

Reading your post again....Where you said the ear muffs slid down and you heard a knocking sound. If you haven't been around these motors alot, the water that comes through the exhaust does make a slight knocking sound. Good luck

problem found, Outdrive

Just hit it with that giant wrench you are holding. That should fix it.

Seriously? Upper?

I wish someone would hit me with the dam wrench , Maybe I would smarten up and get out of this hobby.

Yes , seriously.