Changing Merc 90hp 4 Stroke driveshaft seal

[Willhound]

While recently changing the water pump impeller on my 2011 90 HP Merc 4-Stroke I noticed some wear from the upper seal on the top end of the driveshaft. Area is just a few inches below the upper spline on the shaft. You can just barely feel the ridge with your thumbnail.
Asked at a local Merc dealer about how involved a job to at the very least change out the seal, and even possibly the shaft if necessary.
He related that he had never had to change one of those seals, and wasn't sure if it might not require pulling the entire power head off......
That sounded odd to me. Is it really that difficult? Costly fix?

 

[racerone]

Are you sure this is wear from a seal ?

 

[Willhound]

No Title

Pretty sure. With the foot off, if you shine a light up towards the bottom of the powerhead where the spline on the drive shaft engages, you can see it. You can also feel it as you feed the driveshaft back up into place when replacing the foot. 17 on the schematic I think?

 

[racerone]

Any more really close up pictures of the area that is " worn "

 

[Willhound]

No Title

Don't know if this is any better. Closer but taken on other side of shaft. Groove is not as evident in this one.

 

[racerone]

You would think that a groove from wear would be the same all around.-------Any chance that this groove is an imperfection from a manufacturing process ?-----Is the top of the shaft chrome plated ?-----I am not there to look at this first hand.-----So questions need answers.

 

[Willhound]

"You would think that a groove from wear would be the same all around" - I agree...part of what is baffling me. Can't see it being a manufacturing defect, it's the only mark on the entire shaft, and would be a huge coincidence if the only imperfection happened to be where the shaft sits in the seal. The top of the shaft is splined, can't tell if plated or not.

 

[Willhound]

Anybody else have any experience changing out this seal, or seen this kind of mark on the upper driveshaft? Am I worrying about nothing??