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Merc 350 engine noise help needed

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LakeMike

New member
I have a tapping / clacking noise at idle coming from my port engine on my 2014 327SSX Chaparral. The mechanic at my marina looked at it but couldn’t diagnose anything - they want to start taking things apart to “get a better listen” but I am leaning towards getting a second opinion before letting these guys go any further. Here are the symptoms:

- tapping / clacking noise that seems to be isolated to the rear port side. The mechanic tried pinpointing the source and so have I with a stethoscope but no luck.
- very consistent rhythm
- does not occur at cold. Only after the engine is warm does the sounds start
- the noise is there at idle ~600 RPM. the sound goes away when throttle is increased above ~800 RPM.
- marina mechanic ran a code scan and found no issues; said the run history looks good. No over heats, no high rpm abuse.
- no performance problems. Runs smooth at both low and high speed.
- first noticed this noise when I was in the engine compartment doing an oil change last fall when I put the boat away. I put in 25-40 synthetic blend Merc oil.
- the engine is 2014 with ~120 hours
- Merc 350 with catalyst

I am hoping the fact that it doesn’t make noise until the engine warms up and goes away when above ~700 RPM will help narrow this down for someone with right experience and skill to help point me in the right direction.
 
Sounds like a lifter to me pull the valve covers and adjust the rockers and see if it cures the issue. If not you may have a lifter on its way out. Is the oil pressure good when it starts ticking?
 
kimcrwbr1 said:
Sounds like a lifter to me pull the valve covers and adjust the rockers and see if it cures the issue. If not you may have a lifter on its way out. Is the oil pressure good when it starts ticking?
Click to expand...


Oil pressure is 40 at idle and 60 up on plane 3500-4000 RPM. That is the same as the starboard engine. I do see some fluctuation in the gauge needle between 55-60 while on plane but that may just be the gauge.
 
I have the same noise , or at least mine is very faint, only after warmed up. Only at idle, I think it the exhaust shutter vs valve train noise. Cant hear it at WOT...
 
- the noise is there at idle ~600 RPM. the sound goes away when throttle is increased above ~800 RPM.
Click to expand...

Ayuh,..... I'm guessin' the rubber was burnt off the shutter, 'n now it's clickin', metal to metal,.....
 
It doesnt make it bad possibly you have a slight miss at idle speed causing a pulse allowing the flapper to slam shut? When was the last tuneup? Do a cylinder drop test and see if its firing on all cyls after warmed up?
 
Good suggestions regarding the drive coupler damper springs (if In Board transmission) and/or an exhaust back-flow prevention flapper.
But lets say that these are not the source.
Does this noise sound as though could represent a possible cracked piston (i.e., piston slap), or does it more so represent rocker arm clatter (i.e., excessive lash)?

Suggestion:

With the engine running while in the temp and rpm range where this occurs, remove one spark plug cable from the distributor cap.
This will not cause a shock to you if you hold the cable only!

See if the removal of one or another cable has an effect on the noise!
If if does, check the two cam follower adjustments for that cylinder.

If not, it could/may be piston slap.


.
 
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Here is a link to a video I put on youtube. Starts with the engine at ~800 RPM then I drop it to 600 RPM and the noise starts up.

Does this sound like exhaust flappers?

 
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LakeMike said:
Here is a link to a video I put on youtube. Starts with the engine at ~800 RPM then I drop it to 600 RPM and the noise starts up.

Does this sound like exhaust flappers?

Click to expand...

Get some tools and loosen the belt tensioner and take the belt off. Start the engine and see if the noise goes away. No worries you can run the engine with out the belt to check it, just mind the temp. Diagram for belt routing will be on the t-stat housing.

When was the last time the water pump impeller was changed and the pop-it and diverters checked/serviced?
 
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Docksidemarineservices said:
Get some tools and loosen the belt tensioner and take the belt off. Start the engine and see if the noise goes away. No worries you can run the engine with out the belt to check it, just mind the temp. Diagram for belt routing will be on the t-stat housing.

When was the last time the water pump impeller was changed and the pop-it and diverters checked/serviced?
Click to expand...

Thanks for the input.

I did run without the belt on and the tapping noise is still there. I’ve only owned the boat 1 season and have not changed the impeller yet. What is the pop it and diverter? Same as the exhaust flapper or something else?

Did the video work for you? Does that sound like it could be the flappers?
 
LakeMike said:
Thanks for the input.

I did run without the belt on and the tapping noise is still there. I’ve only owned the boat 1 season and have not changed the impeller yet. What is the pop it and diverter? Same as the exhaust flapper or something else?

Did the video work for you? Does that sound like it could be the flappers?
Click to expand...
Flappers usually rattle with no frequency. Your tapping is constant.

Definitely sounds like valve train noise. Actually your engine sounds terrible, like a sewing machine.

Your noise goes away with a slight increase of oil pressure and comes back when it goes below 40psi(according to your video)...

The noise is not there when the engine is cold because the oil pressure is elevated from cool oil.

Remove a quart of oil and add a bottle of Lucas to it. This will bump your oil pressure, it is not a cure for your problem. Make sure you do not over fill the oil.

I hate to say it, but this engine will be coming out of your boat. Pull the oil filter and cut it open and inspect it with a jewelers loop ....This will confirm it.
 
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Almost sounds like a leaking spark have you run it at night and looked for fireworks? A exhaust leak can also make a snapping noise. Get a three foot length of vacuum tubing and tape a soft wier on theend leaving the jole open. Put one end in your ear and search around the manifold gaskets listening for the leak. Do the cylinder drop test at the distributor and see if it responds to pulling a plug wire? I would use a good pair ofinsulated pliers that ignition can give you quite the jolt. That sounds like a snap tom
me. Had a jeep make that noise ended up being the exhaust manifold gasket exact same senario only after it got hot.
 
Docksidemarineservices said:
Flappers usually rattle with no frequency. Your tapping is constant.

Definitely sounds like valve train noise. Actually your engine sounds terrible, like a sewing machine.

Your noise goes away with a slight increase of oil pressure and comes back when it goes below 40psi(according to your video)...

The noise is not there when the engine is cold because the oil pressure is elevated from cool oil.

Remove a quart of oil and add a bottle of Lucas to it. This will bump your oil pressure, it is not a cure for your problem. Make sure you do not over fill the oil.

I hate to say it, but this engine will be coming out of your boat. Pull the oil filter and cut it open and inspect it with a jewelers loop ....This will confirm it.
Click to expand...

Thanks Chris. That’s not what I want to hear but it makes sense what you are saying about it being tied to oil pressure. I’ll try the Lucas oil treatment and see if I can buy some time until I find a shop to dig into it further.

Question on oil treatment - my motors are the newer Merc catalyst version and ive been told to be careful to with oil selection... is okay to use the treatment?
 
LakeMike said:
Thanks Chris. That’s not what I want to hear but it makes sense what you are saying about it being tied to oil pressure. I’ll try the Lucas oil treatment and see if I can buy some time until I find a shop to dig into it further.

Question on oil treatment - my motors are the newer Merc catalyst version and ive been told to be careful to with oil selection... is okay to use the treatment?
Click to expand...

Lucas is designed to work in all catalyst engines. You have to use Catalyst oil in your crank case...Quick Silver 25w40 Catalyst oil.

The lucas will not fix your issue. It will increase viscosity and if the noise goes away after adding it, you will know what your issue is.

Sorry to say, it will not "buy" you time.

Like I said before, your engine sounds like a sewing machine.

If the Lucas stops the noise, it is important to dig into your engine and possibly just do a repair vs a replacement long block.
 
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kimcrwbr1 said:
Almost sounds like a leaking spark have you run it at night and looked for fireworks? A exhaust leak can also make a snapping noise. Get a three foot length of vacuum tubing and tape a soft wier on theend leaving the jole open. Put one end in your ear and search around the manifold gaskets listening for the leak. Do the cylinder drop test at the distributor and see if it responds to pulling a plug wire? I would use a good pair ofinsulated pliers that ignition can give you quite the jolt. That sounds like a snap tom
me. Had a jeep make that noise ended up being the exhaust manifold gasket exact same senario only after it got hot.
Click to expand...


You cannot do any of these tests on an EC engine you will damage the catalytic convertor. If you are looking for a dead hole on an EC engine you can ONLY pull injector plugs and shut fuel off to the cylinders.

If a plug/wire was loose the PCM would register it as a misfire and set a code.
 
Thanks again for everyone's input.

I plan to put the Lucas oil in later today and I'll report back. By the way, Chris I see there are a few different products - do you suggest the "Heavy Duty Oil Stabilizer" or the "Pure Synthetic Oil Stabilizer" or something else? I currently have Mercury 25-40 Synthetic blend in the engine.
 
Docksidemarineservices said:
I'd test with the HD oil Stabilizer.

https://lucasoil.com/pdf/TDS_HD-Oil-Stabilizer.pdf
Click to expand...

I snuck away from holiday festivities and tried the Lucas oil. Ran for about 15 minutes, (clacking started same as before) drained a quart, added the oil ran for 20 minutes... clacking still there. Same as pre Lucas.

So what do you make of that?

Here is a new piece of info - I took the belt off for a minute to troubleshoot the moaning/whining noise you can hear from the pulleys in the video I linked before. That noise is gone when the belt is off. Clacking is still there but it doesn’t sound “like a sewing machine”. I rotated each pulley by hand and the one making the noise is the big one in the center (water circulation pump, right?). When I called mercruiser a week ago to ask about warranty coverage the customer service guy checked my serial numbers for any service campaigns. He found the sea water pump had a campaign for serial numbers near mine. I’m not in the range but close and he said sometimes their ranges are not perfect.

I will be searching for a good mechanic in my area (Lake St Clair - Michigan) but in the mean time this site has given me more good feedback than the mechanics at my marina have so I appreciate your feedback.
 
Sea water pump and circ pump are two different pumps.

Glad that the sewing machine noise disappeared with the belt removal.

I would suspect you have a failing lifter in the valve train. The noise goes away with a slight raise in oil pressure. If your Oil Gauge is close to being correct, you oil pressure seems a little on the low side, but still withing spec. The lucas was just a test to see if the oil pressure would come up and quiet down the noise.
 
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