Define- Propeller drop.
The propeller shaft in the aft peak tank is provided with inboard and outboard seals. These seals contain nitrile rubber or viton lip seal, which seals against the cast iron propeller shaft. After a few years it creates grooves on them and naturally looses sealing and sea water easily find its way inside. This reduces the lubrication effect and creates wear in the bronze liner. Now there is enough clearance the shaft will come down by certain amount because of propeller weight. This drop in propeller shaft is termed as propeller drop.
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