Knocking Noise From Lower Unit

mwover

Recruit
Joined
Aug 19, 2013
Messages
2
Have a 1996 Murcury Force 120hp. Hearing a load knocking noise from the lower unit while moving forward. Do NOT hear the knocking noise while in Neutral or Reverse.

What could this be?

Thanks for any help

Mike
 

MickLovin

Master Chief Petty Officer
Joined
Feb 18, 2013
Messages
822
Re: Knocking Noise From Lower Unit

Check the prop tightness, it may be missing a washer or spacer.
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
18,183
Re: Knocking Noise From Lower Unit

More than likely the clutch dog's worn.
Possible the linkage or cable needs adjustment(hope this is it).
Take the shift linkage off and shift by hand.
If it does it then the lower needs to be taken apart.
Post pics of the dog(both sides) when you get it out.
The 97 with OEM doesn't have a washer on the nut side.
If he's missing the thrust hub he'd be chewing up the lower and doing lots of grinding(probably wouldn't hear it as it's under water)
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
18,183
Re: Knocking Noise From Lower Unit

More than likely the clutch dog's worn.
Possible the linkage or cable needs adjustment(hope this is it).
Take the shift linkage off and shift by hand.
If it does it then the lower needs to be taken apart.
Post pics of the dog(both sides) when you get it out.
The 97 with OEM doesn't have a washer on the nut side.
If he's missing the thrust hub he'd be chewing up the lower and doing lots of grinding(probably wouldn't hear it as it's under water)
 

Jiggz

Captain
Joined
Oct 23, 2009
Messages
3,909
Re: Knocking Noise From Lower Unit

The only difference between reverse and neutral is which clutch dog engages. Since there is no noise in reverse, it tells you the forward dogs are either worn out or not fully engaging due to misadjusted linkage.
 
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