knocking noise in lower unit

[sgtzro]

I have a 1996 Evinrude 70 HP outboard, engine runs great, but I started hearing a knocking noise from the lower unit. Now it seems to be getting louder. The sound is most noticable upon acceleration and deceleration and seems to be a harmonic sound. Can anyone help diagnose the problem short of replacing the unit?

 

[S.T. Marine]

Re: knocking noise in lower unit

Can you tell if its commming from the lower or propeller??? might just be the prop

 

[sgtzro]

Re: knocking noise in lower unit

The knocking sound is defintely coming from the lower unit gearcase. I drained the gearlube and on the magnetic lower plug there were lots of metal shavings, I am going to try to drain and flush the unit to see if that helps.

 

[ob]

Re: knocking noise in lower unit

shift rod may not be fully engaging pawl and causing excessive back lash in mating gear surfaces.put motor in gear while not running while someone slowly turns prop to assist engaging.then hand operate the prop right and left and see if you can feel slop in gears.

 

[slow_boat]

Re: knocking noise in lower unit

LOTS of shavings = serious problem = more its run = lots more damage. Take it apart & find the problem...may alraedy be too late.