replaced driveshaft; weird rubbing noise

[GunsAus]

Hello everyone,

I had a mechanic friend of mine (who has worked on outboards for a while) replace the driveshaft in my 50 ELPTO 2 stroke 3 cylinder after I hit a rock and it broke near the water pump. After taking everything apart, we did not see anything else but the driveshaft (which snapped cleanly) else out of the ordinary. Later on, I measured the runout on the prop shaft and it does seem to be out of tolerance. We installed a used driveshaft off ebay that appears to be straight and in great shape. We also replaced several gaskets, seals, and lube gear. No metal savings were seen by the way. We did not replace any bearings or races as (again) they appeared to be ok. Ever since when running at idle there is a rubbing noise which seems to (increase and become higher pitched when accelerating) and to be coming from driveshaft area, but we cannot find the problem. We've had it apart three times now, searching for a bad bearing etc. and can't find anything. I am attaching a short video. Any ideas/help would be greatly appreciated!

 

[DeepCMark58A]

Dumb question but did you inspect the upper connection point of the drive shaft to the power head?

 

[Faztbullet]

Did you check the shimming as manufacturing length differ....sounds like it to tight.

 

[GunsAus]

I have wondered about both of these possibilities. DeepCMark58A I don't think we looked at where the driveshaft connects to the powerhead as its still pretty tucked in even after you take lower end off. Faztbullet We have the factory manual and there is nothing in there about shimming and it specifically says: no adjustment for backlash under the specifications. Thank you for the replies, keep the ideas coming..

 

[Faztbullet]

You better get a better manual as it takes special tools 91-14311A2.91-817057 and 91-19660 to set driveshaft preload.....never seen a Merc unit that wasn't shimmed.

 

[GunsAus]

So I called the local Tracker dealership, gave them the outboard serial # and asked them to verify through their computer system if this motor required shims. They told me they couldn't find anything and that this is maybe one of the few Mercury's that doesn't take shims.

 

[GunsAus]

At this point I'm guessing the small bend in the prop shaft (need a machinist dial to see it) is enough to cause the vibration/noise.