Hi guys, back on deck after spending a couple of weeks 4wdriving around the Hervey Bay area and Fraser Island - an amazing place!

I have a bit of a problem with the through hull shaft seal - it's not leaking, but there is a black line that has appeared on the bilge matting. It seems to have been "flinging off" the mechanical seal.
I first noticed a whining sound when the engine revs were over 1800 rpm (I normally run at 1500 - 1600rpm). When in neutral there is no whining sound.
So I'm thinking the mechanical seal is wearing away and is in need of replacement. To do that, it would mean taking her out of the water I guess.

Can any of you knowledgeable people give me some idea if I am on the right track please?
I can probably post some pics if it helps.

Cheers!