Mercruiser 496 mild tapping

[HallOfDreams]

hey everyone,
I have twin 8.1 494’s and have feint tapping coming from one bank. If you put your ear to the riser you can hear it more noticeably. I think it’s coming from a lifter. Anyone else experienced this? Worth the expense replacing or just expected on 700 hours?
Thanks.

 

[scoflaw]

Could be an exhaust leak

 

[douglee25]

Does the sound go away when in gear? 496s are known for being finicky on plugs and wires causing misfires... Especially at idle.

 

[HallOfDreams]

Does the sound go away when in gear? 496s are known for being finicky on plugs and wires causing misfires... Especially at idle.

Did not try that to be honest. But both engines very smooth and pulls well.

 

[douglee25]

Did not try that to be honest. But both engines very smooth and pulls well.

10-4.

If you do a search around here you'll find several threads for chattering or noises at idle with 496s. Most have been traced back to bad plugs and wires.

 

[HallOfDreams]

Only thing I would counter is that it still does it with revs. Although quieter which i put down to other general noise drowning it out. But worth adding to the investigation list

 

[douglee25]

It's possible something is up... Try the plugs and wires and then report back. When was the last time they were done?

 

[HallOfDreams]

It's possible something is up... Try the plugs and wires and then report back. When was the last time they were done?

Only just got the boat. The plugs were reported to be slightly worn when compression testing.

 

[douglee25]

All compression readings good?

I'd do a tune up to get a baseline on your equipment.

 

[HallOfDreams]

All compression readings good?

I'd do a tune up to get a baseline on your equipment.

Yep really good

 

[Spark600]

I just went thought this on my 08 496
It sounds like a rocker tapping on my starboard motor, port side of the motor I used a mechanic's stethoscope to determine that the sound is coming from the stainless steel exhaust elbow, not sure why.
I did do a compression test on both motors and I have reading from 176 to 179 on all the 16 cylinders.
I also do oil samples ever year and they have came back with excellent numbers and comments.
I changed all plugs and wires and still have that little noise.
I will continue to monitor this as well as do the oil samples.

 

[HallOfDreams]

I just went thought this on my 08 496
It sounds like a rocker tapping on my starboard motor, port side of the motor I used a mechanic's stethoscope to determine that the sound is coming from the stainless steel exhaust elbow, not sure why.
I did do a compression test on both motors and I have reading from 176 to 179 on all the 16 cylinders.
I also do oil samples ever year and they have came back with excellent numbers and comments.
I changed all plugs and wires and still have that little noise.
I will continue to monitor this as well as do the oil samples.

Yep identical to mine. So far technician thinks it’s a lifter.

 

[El Capitan]

“Ticking” usually describes a noisy lifter. Exhaust oftentimes described as a “tfft tfft tfft”.
Knocking usually a piston slapping.

 

[HallOfDreams]

“Ticking” usually describes a noisy lifter. Exhaust oftentimes described as a “tfft tfft tfft”.
Knocking usually a piston slapping.

Definite tick can be described as oily sounding.

Can this be left? Engine is fine otherwise.

 

[El Capitan]

It should be accurately diagnosed. A ticking lifter won’t get better over time.

Their is ticking and there is TICKING. That is the sound of metal on metal.

Do a search on YouTube and decide.

Good luck!

 

[douglee25]

If it sounds like a sewing machine, it's fairly normal valve train noise.

 

[HallOfDreams]

If it sounds like a sewing machine, it's fairly normal valve train noise.

Ok so I think we have established a slight bit of lifter noise. Is this common. On 496’s? Or mercruiser in general? I had a mercruiser with 100 hours on it and made same noise same side too.