My post type code:

function yacht_post_types($post_types) {

$post_types['yacht'] = array(
      'labels' 			=> piklist('post_type_labels', 'Yacht')
      ,'title' 			=> __('Όνομα σκάφους')
      ,'menu_icon' => 'dashicons-sos'
      ,'capability_type'  => 'post'

      ,'supports' 		=> array(
        'title'
        ,'revisions'
        ,'thumbnail'
        ,'editor'
      )
      ,'public' 		=> true

      ,'taxonomies'		=> array('category', 'manufacturers')

      ,'has_archive'	=> true
      ,'rewrite' 		=> array(
        'slug' 			=> 'yacht'
      )
      ,'edit_columns' 	=> array(
        'title' 		=> __('Name')
		,'post_states' 	=> __('Status')
      )
      ,'hide_meta_box' 	=> array(
        'slug'
        ,'author'
      )
      ,'post_states' 	=> true
    );

    return $post_types;
}

add_filter('piklist_post_types', 'yacht_post_types');

function yacht_rewrite_flush() {

    // codex_yachts_init();

    yacht_post_types();

    flush_rewrite_rules();
}

register_activation_hook( __FILE__, 'yacht_rewrite_flush' );