2014 yamaha f90xa bottem end noise

[Borutskis]

So ill be honest ive been pretty hard on my bottem end since ive owned it. Have had a aluminum prop the entire time, ive hit a ton of rocks on the prop and its quiet damaged. Changed the impeller the other day and ran the motor up in the driveway and in forward and reverse gear you can hear a chatter coming from the bottem end. Put my mechanic stethescope on it and you can definetly hear uneven gear noise or bearing noise either from the bearing carrier or from the front roller bearing. Changed my gear oil last year and dropped the oil yesterday after maybe 10 hours on the motor this year and it came out very dark but nothing more then glitter came out, no solid pieces. I looked at the prop for wobble and there is a little bit of wobble. I run the motor without a prop and the noise goes away. Bought a new prop and the noise is still there. Is there a spec for runout on these prop shafts to see if its out of spec, im assuming the bearing are wearing and puting any load on them are whats causing the noise. With the bottem end off and in gear as i spin the prop shaft by hand there are no rough spots felt on the gears and they it spins smoothly atleast. Theres no play in the propshaft as it still feels solid. I also noticed a wear mark or polishing on the shaft where the bushing sits, but its not getting that classic yamaha chirping noise. I gotta order the retaining nut wrench so wont have it opened up for a couple of weeks. If im just replacing the bearings do i also have to remeasure the backlash on the gears or just slap the new bearings in and away i go. Am i missing anything else i should be checking or just open it up and go from there

[ausnoelm]

I think you might be chasing ghosts……are you sure there’s something wrong?

[TownsendsFJR1300]

If your engine is like my F150, when installing the impeller, you should PULL UP ON THE DRIVE SHAFT when installing the retainer.

It takes out the slop and takes away any noise (similar to yours).

.

[Borutskis]

What is the retainer you speak of from the attached pic

[panasonic]

If you are just replacing prop shaft bearings you shouldn't have to worry about your backlash...it should remain the same. Just keep track of the shims that are in there and where they go.

That front bearing is a tapered roller bearing and getting the race out can be troublesome for sure.

Are you also going to replace the drive shaft bearings as well? Check you service manual as they need to be installed a certain distance down in the bore. I would measure that before driving it out. Really need to have a proper Yamaha service manual to be tearing apart lower units.

[TownsendsFJR1300]

Just looked up your specific model/year and you don't have the retainer I spoke of..

Good luck..

.

[Borutskis]

Went over to a buddies who has a 2017 yamaha f75 and listened to his and what do you know same noise. Last trip I was towing a tube with 3 people on it plus has 6 people j the boat. So maybe I am just chasing ghosts ha. I attached what the gear oil looked like after that trip so I guess it's normal wear and tear on the gear oil after pushing this motor this hard. Iv also attached a pic of my middle casing as it's not aligned anymore.
Don't know if this would affect drive shaft positioning and something i should be worrying about. Also on my buddies boat there isn't a middle casing like mine but his bottom end doesn't quiet like up also so don't know if this is common on yamahas

[panasonic]

Should be a dowel pin on mid section to line up the cases...

[Borutskis]

Yeah that's what I thought. Took the mid section off and the dowels are still there. Took the dowels out and there not gaped or anything. I'm boggled how the case would twist and misaligne itself

[Borutskis]

I'm just speculating here but what I think I'm hearing is the slop in gear of the pinion gear. The noise goes away once I throttle it a little bit so through centrifugal force pushing the driveshaft downwards and meshing the pinion to the gears. I put a magnet in the gear oil and nothing came out. Plan on just running the motor until the fall and changing the oil. If it comes out the same dark color I'll have to open her up

[panasonic]

That oil is awful black with only 10 hours on it. Was there a shine on the surface of the oil in the container? I would change out that oil again and see what it looks like now.
You say you are going to keep running it like it is? It is a lot easier to fix things before it goes kaboom then after....just saying.

[Borutskis]

No real shine was noted, but I dumped it in a container already. The only thing I noticed at the bottom of the oil was a silver colored paste somewhat. Got stuck somewhat on the magnet