Terrible sound from my 9.9

[hoeser]

Last night I went to check on my inflatable which is powered by what I believe is a late 80's Mercury 9.9 (S/N: 0B164747). Top end runs terrific and always has although I got the motor second hand. It runs perfectly in forward but in neutral or reverse there is a terrible whirring sound, almost a grinding sound.

I immediately removed it from the boat and drained out the lower unit oil, which I'm afraid to say had quite a bit of metallic dust and even a small number of larger metallic particles in it. I have not yet started disassembling and I was hoping I could get some advice on what it could be / what to look for and any other useful information.

Thanks in advance!

-Dave

 

[green4themoney]

Re: Terrible sound from my 9.9

to understand whats happening here you have 3 gears in your LU a pinion, a reverse, and a forward, and you have a clutch dog which is slid to either the reverse gear or the forward gear to engage it.... the clutch dog is connected to the prop shaft via splined teeth... as for shifting there are a few variation but they all absically have the same idea.... now as for what happened with yours, it almost sounds like your clutch dog wasnt fully engaging the reverse gear... cause if it stated fine, and ran fine in forward the position of the gears doesnt seem to be the issue here (because as soon as you start the motor the pinion gear is spinning both forward and reverse gears) or you also may have had a broken gear.... the LU is going to have to be dissambled now to further inspect the damages and the cause, i believe ure gonna need some special tools as well.

i dont know if you did this or not, but it is never overemphasized enough that when your shifting, never shift slow, almost "snap" your shift lever in the selected gear so the clutch dog engages with the gears properly and reduces your chance of wear or your gears corn flaking, and alson make you are at idle speeds while shifting.... in the near future.... but sounds like you may of had a little problem here and a mishap you seem like a knowledgable guy...

 

[hoeser]

Re: Terrible sound from my 9.9

I never shift slowly because I understand the stress that places on the lower unit, so that is not the issue here. Again, I must stress it whirrs/grinds in neutral as well as reverse and once it is engaged into the forward gear it sounds as if everything is normal and preforms as such. I've also never shifted at anything but idle, and this engine has a magnificently low idle, it's really quite awesome, it couldn't be more than 450-500rpm. It really does run tip-top aside from this lower unit issue.

I'm curious to know which special tools I will require though to get this apart?

I'm mechanically inclined enough to take on the repair, I've done top end rebuilds before. I'm currently waiting on the arrival of a service manual so I don't have much to go on aside from some exploded part diagrams right now.

 

[green4themoney]

Re: Terrible sound from my 9.9

im sorry i must have misread that it made the wirring in neutral and reverse... but not forward, if your engine is a 9.9 it must be an 86 or newer, and thats a really low idle possibly a 4 stroke? anyways you will see a hub in the gearcase housing on the LU and it is reverse threaded... now im not completely sure there are a few variations depending on the year of your motor... once that is removed you will be able to get to your seals to remove them and have acess to your prop shaft and gears, the pinion will also have to be raise i believe to remove the guts of the LU, again there are a few diff set ups depending on your year, but if you have a good understanding of things and you are mechanicaly inclined... the exploded diagrams you get will be more then enough... im not a gambling man but now it sounds like to me that your forward bearing is gone.... because the only time the forward bearing isnt spinning freely is when its engaged with the propshaft (when your in forward) when in neutral the forward bearing spins freely and in reverse your forward bearing spins the opposite way the propshaft is spinning and thats the only time you are hearing the whirring....thats how i would diagnose it myself, but once you pull out the assembly let us know whats up take a few pics if you can....

 

[hoeser]

Re: Terrible sound from my 9.9

Tore it down last night, needs at minimum a pinion gear, a forward gear, the bearing kid behind the forward gear, and a new carrier housing because its cracked, looked to be that way for some time too. I also got a great deal of shellshock with mercury parts pricing. Oye. Anyone have a used lower unit for a 87' 9.9?