STRANGE SOUND FROM 3.0 MERCRUISER

[Mustangman 52]

i just did new wires and plugs its been converted to electronic ignition so no points. i didn't set the timing with a timing light i tried retarding it a little no change i have no timing light .i know the timing can ping if to advanced but can it rattle like this?

 

[Eric 3.7LX Alpha 1]

Timing is very important... it deserves a check to eliminate it.

 

[Mustangman 52]

ill borrow a timing light and set it.

 

[flyman219]

You might try pulling one spark plug wire at a time while the motor is running to narrow down the search. If you have a rod or piston issue I would think the noise would change when the spark was removed.

Mike

 

[Mustangman 52]

ok timing is set still idles rough.i pulled one plug at a time, no change in the sound.i tried a rubber hose instead of stethoscope to isolate the noise.it is difficult for me to tell but it does seem to rumble around the timing cover i remember having a trouble at one time with this on and old 350 engine does that sound like it may be a stretched timing chain to anyone?

 

[Mustangman 52]

from what i can tell from search is these are gear sets no timing chain.i am out of ideas.rebuild?

 

[Mustangman 52]

?

https://www.youtube.com/watch?v=C5r6...ature=youtu.be

 

[Mustangman 52]

any ideas on the noise no one has heard this before?

 

[fishrdan]

Use a 3' section of heater hose held up to your ear, and them moved around the engine, to pin-point where the noise is coming from.

My SWAG would be the rear engine mount is loose against the engine or the tin access cover on the front side of the flywheel as BT mentioned.

 

[Mustangman 52]

ok i well give it another shot and listen again i am really having trouble with the hose i have been all over the engine it seems the noise is coming from around the timing gear cover i put it right on the flex cover no sound from there. i well check around the mount in the rear.could this be the fuel pump?i don't hear noise when i put the hose on it but its close to the timing gear cover.

 

[flyman219]

I wish I could tell you what it is other than a serious sounding knock. As loud and sharp as that is you might be able to feel it if it was the fuel pump by placing your hand on it while it's running.

You might get a cheap mechanics stethoscope (HF) to see if that helps seeing as the hose and wood stick didn't do the trick (I like the stick method myself). Remember you are just looking to locate the closest moving part to the source of the knock. If you're by the timing cover you have the number #1 cylinder, timing gears crankshaft bearings, balancer, pumps etc in the neighborhood as suspects. From the clip it looks like the engine twitches with each knock seeing the coil moving.

Mike

 

[flyman219]

Might loosen the belts and take those pumps out of the picture for a test.

Mike

 

[Mustangman 52]

i took the belts off its not the alternator or water pump i eliminated already.it does sound serious to me to. i cant use the boat until i know what it is alaska summer is short.i may have to take it to the pros.if they can even get a look at it this time of year.

 

[Mustangman 52]

as for the shake the motor was cold it runs smoother once its warmed up.but never runs as smooth as i feel it should compresion was 120 120 120 #4 105 i figure that,s why it wont idle smooth.