Clatter in lower unit...

[Waterproof]

As I rev my 1988 115 hp. Merc I-6 I hear a clatter (Sounds like a bolt loose in the cowling) as the motor RPM comes up, then down. I've been told that this is an indication of wear in the gearset, but should I be overly concearned or is some gearset noise normal on an older OB? I only hear the noise when the motor is running on muffs, and there is no noise when running at any constant speed, only as I rev up or down quickly. Out of the water I hear the noise when I rev up out of gear, or in gear. in the water I don't hear it. Again The noise is present only on quick RPM changes up or down, and quiets as the RPM becomes stable again. The lower unit oil seems to stay clean, no major indications of unusuial wear, and the OB performs well otherwise. Thanks for your help.

 

[Repo42]

Re: Clatter in lower unit...

I am no motor goo-roo, but that is how my lower unit started out.. Now I am in the process of taking it apart to survey any damage which is most likely worn out gears or something...

 

[hondon]

Re: Clatter in lower unit...

Your gearcase is equiped with racheting gears that reduce wear and tear on the clutch dog and provide smoother shifting.When you run out of water ,there is no pressure against the prop blades to hold the propshaft against the cogs of those gears ,SO you get alot of noise if you rev it then back off in gear.Why do that anyways?