суда отстоя - это суда, временно выведенные из эксплуатации

http://en.wikipedia.org/wiki/Reserve_fleet
A reserve fleet is a collection of naval vessels of all types that are fully equipped for service but are not currently needed, and thus partially or fully decommissioned. A reserve fleet is informally said to be "in mothballs"; an equivalent expression in unofficial modern U.S. naval usage is "ghost fleet". In earlier times, and especially in British usage, these ships were said to be laid up in Ordinary.

Such ships are held in reserve against a time when it may be necessary to call them back into service, and are usually tied up in backwater areas near naval bases or shipyards to speed the reactivation process. They may be modified, for instance by having rust-prone areas sealed off or wrapped in plastic or, in the case of sailing warships, the masts removed. While held in the reserve fleet a ship will typically have a minimal crew (known informally as a skeleton crew) to ensure that she stays in usable condition—if nothing else, the bilge pump needs to run continuously to prevent the ship from sinking.

When a ship is placed in reserve status, the various parts and weapon systems that the vessel uses are also placed in a storage facility so that if and when the ship is reactivated the proper spare parts and ammunition are available—though, like the ships themselves, these stored parts and equipment are prone to fall into disrepair and obsolescence. For example, during the United States’ 600-ship Navy plan under President Ronald Reagan the US reactivated its Iowa-class battleships to serve with the fleet but, since the ships had not been used since the 1960s, the Navy had trouble finding the various specialty items that were needed to make the ships operational and had to salvage parts from earlier battleships used as museum ships.



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Note added at 42 mins (2010-01-14 21:35:12 GMT)
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Also
http://www.vlagman.ru/slovar.html
Отстой — период, когда судно не выполняет свои функции. Вывод судов из эксплуатации на отстой может осуществляться во время навигации и на межнавигационный период решением судовладельца