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.
".. 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)
1984 Fast/Nicholson 345 "FastForward"