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Join Date: Sep 2005
Location: New Westminster, BC
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Common issue... happens most often when the prop comes to rest on a vertical axis and the lower blade hangs down, with the upper blade in the 'folded' position, both due to gravity.
Slowly turning the shaft from that position often does not provide enough centrifiugal force to properly open both blades. The vibration from this huge imbalance feels like it could tear the strut out, and indeed might do so if allowed to continue at speed.
The 'lower blade dropping' can happen at drifting boat speeds too, that's why racers mark the shaft in relationship to the blades and make sure the prop blades are oriented horizontally so they won't 'fall open' when drifting....
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)