We too have a squeal, but only in a very narrow, rarely used rpm range... and I'm convinced it's from the packing gland.
It does seem to have lessened a bit this season so far and we have no leakage, no other problems so we just avoid running at that rpm.
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)