Mercruiser 3.0 knocking noise with video. Any ideas?

[66bayliner]

Have a complete professionally rebuilt Mercruiser 3.0 long block with a 2.5 head with 25hrs on it which developed a noticeable knock at idle.

Before my last voyage I did a valve lash adjustment which seemed to nicely quiet down the valve train quite a bit. I pumped up the the lifters by turning over the engine without starting and went through the proper valve lash adjustment plus 3/4 and a bit turns on each rocker arm. It seem to run quite smooth until the next time I started it.

I've already done two oil changes and followed all the break in instructions. It's never been a quiet engine so far. The existing 2.5 L I had seemed to run much smoother but the block was cracked. I know these engine can be noisy.

Here are some of the fixes I haven't tried yet.

1) Pulling off the mechanical fuel pump and see if the arm is creating the noise
2) Pulling each spark plug at a time off while the engine is running to determine if one of the cylinders has a problem
3) dirty lifters ??

Any other ideas here??

I'm kinda worried. This shouldn't happen with such a new low hour engine.

Thanks in advance

 

[alldodge]

I would redo the valve lash adjustment.
Back them off one turn each. Start the motor and very slowly back off each rocker some more listening to see if it get worst or stays the same. Once it stays the same for a bit, then start adjusting back down 1/4 turn at a time. When it gets quite, adjust 3/4 more at 1/4 turn between 30 seconds at each adjustment

 

[66bayliner]

Thanks alldodge! I assume once it stays the same for a bit is potentially zero lash ?? I could try that

 

[alldodge]

My thought is there to tight only because it doesn't (to me) sound like a knock. I think there all to tight

Could prove it out quick with a compression test