'Propeller' was the British passage of a single merchant vessel from Gibraltar to Malta (13/19 September 1941).

As the second such undertaking, 'Propeller' followed 'Temple'. The vessel used was the 5,641-ton Empire Guillemot loaded with fodder as civilian transport in Malta was now dependent solely upon horses and donkeys, as did work on the land; these animals also provided a food reserve. Even in normal times, much fodder had to be imported, and in the current siege conditions little could be grown as all cultivable land was devoted to food production for the population.

The ship left the UK in the OG.73 convoy, and was disguised to pass cursory examination as a local French or Spanish freighter. She left the convoy and passed through the Strait of Gibraltar, wearing Spanish markings and escorted by the corvettes Gentian and Jasmine during the night of 13/14 September. She shifted her disguise to Vichy French colours on 15 September until her arrival off Bizerte, where she became Italian and followed the route north toward Sicily. On the final run to Malta she wore British colours and reached the island early on 19 September.

The final part of her passage was difficult as the ship became involved with an Italian convoy which was attacked by Fairey Swordfish warplanes, but the naval aircrew had strict orders not to attack any single ships during the night in question, and these orders were strictly observed even in the circumstances of a night action.

There were then a number of other such single sailings. The 9,653-ton Clan MacDonald sailed independently from Malta on 16 September and, located and attacked by torpedo bombers on the next day, successfully evaded the attack to reach Gibraltar on 19 September.

Empire Guillemot should have returned during 'Halberd' but could not sail as a result of engine defects. She eventually left Malta independently on 22 October 1941 during darkness, but was identified by an Italian torpedo bomber on 24 October and sunk off La Galita island, one officer being killed. The remaining 38 crew and six gunners got away in two boats, but one of these was wrecked in surf when landing on the North African coast and nine more men were lost. Some 33 survivors were interned by the Vichy French.

The 8,039-ton City of Lincoln and 11,168-ton Dunedin Star also sailed on 22 October and proceeded separately to reach Gibraltar without undue incident.

The 7,347-ton Clan Ferguson departed Malta on 24 October 1941 as the final unit in this attempt to clear the harbour of empty freighters. Shortly after sailing she was intercepted and attacked by aircraft off Malta, and as her passage had been compromised at so early a juncture the ship was recalled to the island, eventually to leave in the ME.9 eastward convoy to Alexandria.