STRANGE SOUND FROM 3.0 MERCRUISER

[Mustangman 52]

i have a odd noise coming form my engine.i am familiar with with rod knock and lifter noise, pinging. this sounds like none of them.i well try to get a video of the sound once i put the valve cover back on i inspected the rockers i see no problems.i used a stethoscope can not pin down the noise. its not noisy at idle but as you get close to 2000 rpms it start to rattle not a consistent rattle but almost like something is bouncing around in a cylinder on take off it is not very loud with load. it gets really noisy over 3000 rpm and when letting off the throttle it really clangs. it can idle around the lake all day with no sign of any problems.i know this is not much to go on but any ideas? i am really stuck.

 

[Bondo]

.i know this is not much to go on but

Ayuh,.... Welcome Aboard,.... Not much,..?? more like nothin',....

You said what it ain't, but not what it sounds like,.....

Bein' random, I'll go with a bolt fell out, 'n is bouncin' 'round in the flywheel cover,....

 

[Mustangman 52]

its sound like a bolt bouncing around inside the engine really rattles when i let off the throttle sounds like something is going to come apart.i think a video of the sound is the best explanation.ill get one up here shortly i would really appreciate if someone has any ideas.

 

[poconojoe]

Could it be an exhaust shutter came lose and is clanging around in your exhaust pipe?

 

[Mustangman 52]

it don't sound like its coming from the exhaust but i didn't try the stethoscope there i well check it.thank you.

 

[Bt Doctur]

cracked metal dust cover on the flywheel?

 

[Mustangman 52]

thank you.for trying to help i tried to take a video and of course the first time it is not making any noise on the rabbit ears. ill post back a video as soon as i get it a good video of the sound.

 

[Bt Doctur]

a cracked dust cover rattles like marbles in a coffee can

 

[flyman219]

I'll just toss out a suggestion, I had a performance problem and when it acted up there was a rattling noise from the engine. If your performance has fallen off somewhat take a compression test. You can get a gage at HF for under $30, it would have saved me a bunch had I done that step first. Hindsight is 20/20, #2 cylinder o compression and the motor still idled pretty nice and could still plane out at times. Sure fooled me.

Mike

 

[Mustangman 52]

#4 cylinder is down about 15 pounds from the rest of the engine. idles a little rough not bad i think that is why i cant get it completely smooth.marbles in a can is kinda the sound if they are bouncing up and down would be a good description of my noise but i put a stethoscope on the but dust cover no noise there its not a consistent sound like a rod knock or lifter and it doesn't rattle on take off all the way through it gets noisy at about 1800 rpms and then sounds really awful when getting up to 3000 i when i back off on the throttle, no load it gets even louder?can piston slap or a wrist pin make these sounds.i listened to the oil pan no noise from there valve cover nothing all around the engine i cant pin point it sounds like its from mid point on the engine from the naked ear.i also removed the belt and ran it still same noise. i never heard anything like it.

 

[Mustangman 52]

ok here is the sound of my mercuiser 3.0 any expert ears know what this is?I would sure appreciate some input thanks. https://www.youtube.com/watch?v=C5r6JDBz2ms&feature=youtu.be

 

[Mustangman 52]

its really noisy on the water.

 

[Mustangman 52]

strange sound of my mercuiser 3.0 any expert ears know what this is? video

I would sure appreciate some input thanks.
it get much louder on the water.
https://www.youtube.com/watch?v=C5r6...ature=youtu.be

 

[Alumarine]

You've already started a thread on this topic.

 

[Mustangman 52]

sorry for the new thread but i wasn't sure if people would still look at the old thread i have uploaded video of the sound.

 

[Bondo]

Ayuh,... The link says the video don't exist,....

This is Yer thread, 'bout this problem, so stick with the same thread,....

 

[81 Checkmate]

That dont sound to good. Have you tried to remove the drive, then start it back up. could be the drive unit.

 

[Mustangman 52]

i just resealed the upper drive.i only heard the boat run 1 time before i did the seals and don't recall the noise before. i just purchased this project.it sounds like coming from the engine could that be drive noise?

 

[Mustangman 52]

anyone have any other ideas.i hear the sound coming from the engine, from outside the boat the drive sounds ok

 

[Eric 3.7LX Alpha 1]

Kinda sounds like it's not running on all cylinders... or the timing off.

What's the history on tune up maintenance? Full one with plugs, wires, cap, rotor, points set dwell and timing?