LONDON, December 1 (Reuters): Everton have named former England boss Sam Allardyce as their manager on an 18-month contract, the Premier League club said on Thursday. Allardyce replaces Dutchman Ronald Koeman, who was sacked last month after the Merseyside club dropped into the relegation zone. "I’ve always thought Everton was a great club. Obviously, the club has gone through a difficult spell and hopefully I can put that behind us as quickly as possible and start looking upwards again," Allardyce said in statement. "Ultimately, it’s the ambition of the club, the ambition of the owner and the Board, allied to the fact that it’s Everton and all the fantastic history, which have proved to be key for me." Allardyce, 63, watched from the stands as Wayne Rooney scored a hat-trick in Everton's 4-0 thrashing of West Ham United on Wednesday and takes over with the Merseyside club 13th in the table, five points above the relegation zone. Allardyce's task will be to restore stability and return the club to being the regular top-seven finishers they were under David Moyes from 2004-2013, Roberto Martinez in 2014 and Koeman last season. David Unsworth, who took caretaker charge after Koeman's sacking, will resume as Everton's Under 23 manager and academy director of coaching.