gland, which looks like the image posted below, this is what its innards may look like.

I think trying to repack a gland like this, with the boat in the water, may be quite difficult if not impossible.

Like Tom Brown and others have stated, it may be wise to replace the gland with a conventional bronze gland, or a PSS if have the money, at your first opportunity.

FWIW, I was never able to repack this gland on my H28.5, even with the boat out of the water. I could never find a way to remove the compression washers that separate the rings of packing. What did work for me was to remove the strut, pull the shaft,and replace the gland with a bronze gland that is much easier to maintain and probably a lot safer too.