Engine noise identification

[Sam Sparks]

I have a 38ft SeaRay with dual mercruiser gas engines. I was cruising along and one engine started making this noise. Can anyone tell me what is happening here?

Oct 9, 2026

Shared with iCloud

photos.icloud.com

 

[Sam Sparks]

Here is the engine tag info
MerCruiser MIE 340 (a 454 cubic inch / 7.4L Big Block V8) with 340 Horsepower, serial number A610756

 

[makomark]

maybe a rocker arm is clacking...hard to tell from just a snipet of video..

 

[Bt Doctur]

I agree, rocker arm sounding , If motor performance is still good suspect a rocker arm loose,stud pulled etc. If performance is down suspect a stuck exaust valve,

 

[Sam Sparks]

if it’s a loose rocker arm what does that fix involve?

 

[Sam Sparks]

Not sure about it’s affect on performance as I shut down that engine right away.

 

[makomark]

It depends...won't know until somebody inspects it...

 

[louc]

removing the valve covers and inspecting.

 

[louc]

could be a few things, bad valve lifter (doesn't pump up like it should), bent pushrod/stuck valve, loose rocker retainer bolt, rocker stud pulled out, for a few.
if you are going to go at this familiarize yourself with the procedure for adjusting the hydraulic valve lifters.