Help diagnosing knocking sound in Yamaha SX210

[dwall2181]

Hi All,

I'm doing quite a bit of maintenance due to loss of thrust out of the hole on my 2006 Yamaha SX210 (seems like cavitation - revving rpm's without thrust until I get some speed) and noticed a knocking sound coming from the engine compartment.

Does this sound like a bad mid-driveshaft bearing/s? If so, how do I test the bearings in the mid-driveshaft and cone area?

Just installed brand new wear ring and impellers and also notice my impellers making a lot of contact when running out of the water.

Video 1: video of the noise under the hood
Video 2: video of the impeller hitting the housing at the pump

Any tips to troubleshoot much appreciated!

2006 Yamaha SX210

 

[David Martin]

Old Mechanic trick...........sounds silly but it works an engine stethoscope around 10 bucks or so. lets you isolate a noise. The age of the boat leans towards a worn Mid Shaft or Noisy/worn engine coupler.

 

[Acard7]

if you have a bad intermediate bearing (near the coupler) you’ll most likely have water leaking in while on the lake. What I would do is pull the pumps and run it without the impellers in to see if the noise you’re hearing is just the impeller hitting the housing.

 

[Cobra Jet Steering LLC]

An older trick is to use a stick or hollow tube of p v c or other material and place it in different locations making contact with the engine etc and put your ear up to it to hear where a noise is coming from.
Check your motor mounts and use my trick to inspect the condition of the bearing housing.
Remove the grease fitting on top and use a thick piece of line trimmer string to put down in the grease and inspect what it looks like, If it is bad it will have water in the grease. You also may have bad pump bearings, tip the boat forward on the trailer so the nose is below the rear of the boat, remove the pump cone, inject gear lube into the bearings and then clean the o-ring on the cone, put some silicon sealer on the ring and re install the cone , run it a bit and if it quiets down you may need bearings in the pump. Also look for water in the grease when you have the cone off, and if you want to see if the impeller hitting the liner is causing the noise just spray some WD- 40 or spray white lithium grease on the pump liner and then start the engine if the noise level drops you know what it is.

 

[dwall2181]

Lots of good ideas to try. Will report back.