[bisham]

PROBLEM SOLVED. SEE BELOW. I have a 2001 Miriah Z275 Shabah with a 454 Mag MPI Generation VI.

Have a loud knocking noise. What does an exhaust leak sound like? Someone inside the engine hitting it with a hammer every second?

Here is a link to the noise:

https://www.youtube.com/watch?v=QzJd...ature=youtu.be

Could an EXHAUST LEAK make this sound?

SOLUTION:

It was an exhaust leak. If you ever need to replace your exhaust manifold, risers and elbows on a 454 Mag MPI, do NOT use GLM parts. We put GLM's on ours last year when we did a valve job. Turn out that the exhaust surface area on GLM exhaust systems does not have enough meat to make a good seal. There was one area where only about 1/16" was sealed between the manifold and the head. Also, I ordered a "Stock Mercury Replacement" from a place where we purchased a stainless steel sea water pump, and they shipped us another set of GLM's that I am returning. If you search for new 454 Mag MPI exhaust find the "Quicksilver" brand so you are getting actual Mercruiser parts. They will cost a little more but you will avoid reworking your engine because of the crap GLM manifolds.

[Hudson River Steve]

Unfortunately that's no exhaust leak. It sounds like a rod bearing which is a death sentence for your motor. Better get it checked out by a pro.

Sent from my XT1254 using Tapatalk

[Tlolesen]

Doesn't sound like any exhaust leak I ever heard sounds internal not good 😫

[bisham]

My thought was it sounds like it only does it on one stroke. If it was a rod bearing I would think the noise would be on both the intake and exhaust which would be a faster knock. Does that make sense?

[Hudson River Steve]

It does. Could be a valve that stuck and bent a push rid.


Sent from my XT1254 using Tapatalk