F115 gear case rattle

[fishon162]

I have tried to find an answer to this, and have gone to two different dealers, no one can seem to give me a straight answer.

I have an F115 with stainless steel prop. Approx 200 hours on engine. This spring I replaced the water pump impeller and bought a new 13.25x17 stainless prop.

Since then my motor has developed a rattle or chatter in the lower unit at idle in gear. This happens in both forward and reverse. In neutral at idle it is quiet. It is not a grinding sound going into gear, rather it is a semi-constant rattle sound from the lower unit while in gear.

I have checked the shift linkage and all is fine.

I have been told by some this is normal on Mercs and Yamahas with stainless props.

I have checked the gear oil after 30 hours and no signs of abnormal wear.

Is this a normal or common sound? Any way to stop it short of replacing the lower unit? It is really annoying to me.

[furballs]

have you verified that all of the prop washers were properly seated before you torqued down the prop nut (you did torque the prop nut, right?) ?
it sounds like your prop might be loose or improperly seated .

[fishon162]

Yeah, I have removed the prop and put it back on. I have also removed the lower unit again to make sure the wave washers, etc were reinstalled correctly.

I have even tried different ss props. Only thing that makes the noise go away is to remove the prop completely.

This thing has me stumped.

[furballs]

did it do it last season before winterizing ??

[fishon162]

I don't remember it doing it, I don't fully winterize, just change the fluids in fall and spring, use the boat year round.

My brother thinks I'm crazy, he hears it but doesn't think it is abnormal...he thinks I just notice it now b/c I am worried I screwed something up during the impeller change.

Maybe so, but at the same time I wouldn't think the gears should rattle or really make any noise. Fathers 90 honda doesn't do it at idle.

[furballs]

other than retracing & doublechecking your steps,i'm stumped also. hopefully, one of our fellow members has the answer......