[4] On 2 March 2004, while heading north with barge Bulk fully laden with coal, Herakles ran into trouble in the Bothnian Sea when both of her main engines began to fail in heavy weather.

[9] In 1991 Herakles was refitted with a new bridge and coupling devices by Oy Laivateollisuus Ab in Turku, the same shipyard where she was originally built, and became the third pusher for the Finnish integrated tug barge system, Finnpusku, which is used to transport raw materials to the steel mills of Rautaruukki Oyj.

Propulsion power was provided by two 6-cylinder Ruston & Hornsby ATCM 4-stroke diesel engines, each producing 1,074 kW (1,440 hp), driving two propellers, giving the tug a service speed of 13 knots and bollard pull of 255 kN.

[5][11] Other changes included the removal of the towing winch and installation of a new auxiliary diesel generator, Caterpillar DITA 3512 producing 807 kW (1,082 hp), inside the former cargo hold aft of the superstructure to power the bow thruster of the barge.

[4][10] The remaining towing and salvage equipment was retained for some time after the conversion so that, if necessary, Herakles could perform normal tug duties while not employed as a pusher.

[12] However, it appears that they were later removed completely as the towing gear was no longer listed for Herakles on Alfons Håkans's website unlike with the rest of the tug fleet, making her purely a pusher vessel.

While this upgrade greatly improved her operational capabilities and increased her bollard pull to 588 kN, she still remained underpowered in comparison with the original Finnpusku pushers.

The combination, referred to as Herakles-Bulk, had left Oxelösund, Sweden, two days earlier and was heading north with the barge fully laden with coal.

On 2 March she ran into a storm and the captain, not certain if the vessel could safely be turned around in such a sea state to seek shelter closer to the coast, decided to evacuate half of the crew by helicopter.

In 1990 pusher Finn capsized with barge Baltic outside Hanko, Finland, with a loss of eight lives after her cargo of ore concentrate shifted in heavy weather.

[6] Herakles-Bulk passed the Swedish lighthouse Svenska Björn at 04:00 the following night, encountering only a fresh westerly breeze in which the combination could maintain a speed of 8.2 knots (15.2 km/h; 9.4 mph).

After passing Märketskallen at 10:05 water began to enter the cargo hold over the forecastle and, as the waves gradually grew higher, the speed of the combination continued to drop until it was less than 2 knots (3.7 km/h; 2.3 mph) at 13:00.

When the captain received a report that the starboard main engine was no longer usable he decided to abandon the ship and ordered the evacuation of the remaining crew at 22:16.

The helicopter arrived and began lifting the crew members from the rear part of the cargo hold at around 16:50, a task that was very difficult due to pitching and rolling of the combination.

[6] Although Herakles-Bulk did not declare an emergency or send a distress signal, MRCC Turku asked the Swedish search and rescue helicopters to maintain readiness in case the remaining crew had to be evacuated.

Another Super Puma operated by the Finnish Border Guard, OH-HVG, took off from Turku and, after flying past Herakles-Bulk, landed in Mariehamn to wait with its engines running.

[6] The foundering of Herakles-Bulk was a result of loss of steering ability which was caused by malfunctions in the main engines due to severe weather conditions.

Another possible cause was the development of hairline cracks in the cylinder liner or head due to large variations in engine load, allowing hot exhaust gases to mix with the cooling water.

[6] Since the starboard engine ran normally after it was decoupled from the reduction gear, a likely reason for the sudden drop of engine speed from 1,000 to 270 rpm and subsequent stalling when reconnected was increased load in the propulsion system due to damaged shaft bearing or a foreign object, perhaps something that had fallen from the deck, wedged in the propeller duct, although malfunction in the fuel supply and lubrication system due to the violent pitching of the vessel were not ruled out.

[6] In 1992 the Finnish Maritime Administration issued a wind limit of 14 m/s (31 mph; 27 kn) for Herakles due to the pusher's low engine power and poor performance in heavy weather.

The wind limit was removed in 1993 for cargoes other than the ore concentrate by the Finnish Maritime Administration, but captains were obliged to follow the instructions given by the shipping company.

[6] Swedish Coast Guard detected an oil slick with an approximate diameter of 350 metres (1,150 ft) drifting west of the island of Bodskär on 8 March.

During the following days several vessels of the Swedish Coast Guard arrived at the scene and began the difficult task of collecting and separating oil that had mixed with drift ice.