An emergency tug will provide cover for the Western Isles, Shetland and Scotland's north west coast from a port on Orkney.
Herakles, a specialist anchor handling and towing vessel, will provide the service for the Maritime and Coastguard Agency (MCA).
For 10 years, two tugs were hired by the MCA to provide aid to stricken vessels around Scotland.
The UK government moved to end the contracts in late 2011 before agreeing to short extensions until March this year.
In June, it was announced funding for a tug to work "around Scotland's coast as required" would be provided until 2015.
Orkney Islands Council said it welcomed the move.