Mercruiser 5.7 - noise from the front of the engine

[Broaters]

Hello guys

This is our first post in the engine section so a little background.
We are rebuilding a 21ft searay cuddy cabin link in the signature for those interested. To power the boat we have rebuilt a Merc 5.7 magnum. The engine was first started last year after rebuilt and then stored as the boat was not ready.

We restarted it yesterday with the Y pipe exhaust installed and noticed a noise coming from the front of the engine.

You can hear a rubbing noise like a "shh shh shh shh shh shh" in the background.
I already tried to remove the belt to eliminate an alternator or water pump noise. The noise is still present.
I checked that the harmonic damper is not touching the timing chain cover. no contact.

Would someone have an idea where to look next? I was wondering about any contact of the timing chain with the cover?

or maybe it is just the chain natural noise?

Any help will be much appreciated

 

[tpenfield]

Not much can be determined from a 5 second video.

Maybe try again :noidea:

 

[Broaters]

Not much can be determined from a 5 second video.

Maybe try again :noidea:

agreed, it is more easy when you know what to hear for

here is a longer one

The noise from the exhaust is quite present so I hope you will hear the sound we refer to.

hope this helps

 

[alldodge]

I don't hear anything abnormal

 

[Scott Danforth]

the problem with video is the other background sounds. you really need a directional mic on a video to pick up exactly what your ears discern when standing there.

 

[Broaters]

well I was hoping it could be heard better. maybe on the cutoff in the first video when the explosion noise is gone.
I'll try to shoot another video focusing on this area with the mic.

besides the video, is it normal to get some amount of noise from a timing chain?

do you think it worth removing the timing cover to check if any contact?

 

[Tycer]

A mechanic’s stethoscope is a useful thing. You can make one from a regular stethoscope. You can pinpoint most sounds.

 

[San_Diego_SeaRay]

Do you think it might be a vacuum leak? Why are you keeping the engine at high RPMs? Does it die at low RPMs?

 

[stang32]

take the camera and put it right in the area where you hear the noise. pulling the timing cover on that engine requires lowwerin the oil pan to get the front gasket back in place, not a fun job and if you can avoid it, do so. on the otherhand, you can run the engine for a couple seconds without the cover off as long as the water from the block does not leak into the oil pan.

 

[Bondo]

Ayuh,..... I don't hear anything either,.....

'n I've never seen a timin' chain need replacin', except possibly when doin' a sbc build, from the block, up,.....
Ain't sayin' it never ever happens, but is a rarity,...

 

[tacx]

My 5.7 sounds the same. Has a swish, swish sound. Has been that way since we owned the boat. Three years. No problems.

 

[B Rad G]

Just like tacx, my 5.7 makes a swish, swish sound as well. Right up front. I put a stethoscope on it, but never could hear anything abnormal. Doesn't seem to affect it in anyway. Just my .02. Hope it's the same for you.

 

[Broaters]

A mechanic’s stethoscope is a useful thing. You can make one from a regular stethoscope. You can pinpoint most sounds.

got a medical one at home, will try to use it and let you know.

 

[Broaters]

Do you think it might be a vacuum leak? Why are you keeping the engine at high RPMs? Does it die at low RPMs?

not sure about the vacuum leak how can we test it? spraying brake cleaning fluid around the carb and intake gaskets?

we keep it close to 2000 RPM because the camshaft was replaced and read that a break-in should be done at no less than 2000 for a period of time.

Idle seems ok so far.

 

[Broaters]

will do more tests on the next work session and let you know if we find something.
we'll try to get a more accurate video of this sound

Thanks you all for the inputs

 

[Tycer]

got a medical one at home, will try to use it and let you know.

You can pull the medical end off and use a round piece of metal like a punch or a file or a drill bit in its place. The metal will transmit the sound from a small area.