4.3 v6 alpha 1 gen 2 knocking noise

[Arrowhawk19gts]

Hello folks, first time poster here and apologies in advance if this is a recurring question! I have looked through forum posts but not found a suitable answer, well to my limited knowledge!

I have a problem with a knocking noise at idle and up to 2500 rpm. The noise disappears at this point. It seems to be coming from the rear of engine or outdrive and is more noticeable when engine bay cover is closed.

link to video here at idle https://youtu.be/iyTg1sRrM0Y

and at 2500 rpm https://youtu.be/0c9RmpzJ3ek

longer vid with engine bay cover closed. sorry for poor video skills! https://youtu.be/PeEZehtWRJ4

The leg is in middle in video and turning to full lock either side makes no difference.

I have had boat to local mercruiser mechanic who has taken leg off checked gimbal bearing and u joints and given clean bill of health. Their suggestion was noise from engine due to stainless steel exhausts which are noisier than standard. I still feel that the noise is coming from back of engine or leg?

Any suggestions gratefully received.

Thanks Gordon

 

[Bt Doctur]

sounds like worn exaust shutters banging and you need to correct the rear motor mounts.Spacer is missing

 

[achris]

Yes, sounds like an exhaust shutter. But the port rear mount looked fine to me...

Spacer in place....



Chris......

 

[Rick Stephens]

Might be the shutters, as noted. Seems to me, it should have ruled out the drive entirely that when the drive was pulled you run the motor. With the drive off, just shove a cutoff garden hose in the water passage in the bellhousing, crank the water on and fire up. Knocking or no knocking?

 

[Arrowhawk19gts]

Thanks chaps time to get leg off and will check exhaust shutters