C3/2010M JEANNEAU PRESTIGE 42S, A-58990 (FIN), sinking off Inkoo on 28 May 2010

A Jeanneau Prestige 42S-type planing hull motorboat departed from Espoo in a westward direction Ekenäs as its destination on 28 May 2010. The boat was brand-new and preparations had been made to stay overnight. In Inkoo, on a 5.5-metre fairway, the skipper first decided to turn to starboard, on a crossing fairway, in order to take the motorboat to Inkoo for the night. Immediately after the turn he changed his mind and made a sharp turn further to starboard in order to return to the original fairway after a 270 degree headway change. After the curve had ended, the boat did not, however, return to the intended fairway but instead turned next to the fairway. The boat drove almost with full speed over an under-water shoal whereupon her Volvo Penta IPS drive units hit a rock. This resulted in a serious, uncontrollable leakage and the boat sank next to the fairway. There were three adults and five children onboard the boat and they were rescued to other boats located in the vicinity. There were no injuries to persons, but the boat was completely destroyed. The investigation concludes that the grounding was not caused by any technical failure, which means that the loss of situational awareness after the turn with high speed can be regarded as the immediate cause of the accident and the sudden change in the voyage plan as a contributing factor.

The drive unit did not break off in a controlled way so that the hull of the boat would have remained watertight, but instead the impact caused by the collision broke the weakly-constructed hull of the boat. The boat did not have watertight compartments and the water which flooded into the engine compartment spread into the whole boat which then sank rapidly.

A similar accident occurred the same summer of 2010 when the chartered boat IDA 1 ran aground with similar effects . Both accident boats were equipped with two Volvo Penta IPS drive units. Because not a single of the three drive units which hit a rock broke off in the manner specified by the manufacturer, it was decided that factors related to the structure of IPS drive units would be studied in co-operation by both investigations. Problems were found in the strength pyramid of the drive unit and in the integration of the drive unit and the hull.

The construction of Jeanneau Prestige 42S was found out to be weak at the joint between the transom and the bottom, and the joint of the IPS drive unit and the hull carelessly and poorly completed. The visibility from the wheelhouse on this kind of a boat was also found out to be restricted when the roof hatch is closed.

As a result of the investigation, the Safety Investigation Authority recommends that boat construction regulations are changed in such a way that boats similar to the accident boat remain afloat after the engine compartment makes water, that Volvo Penta check the functioning of the strength pyramid of the IPS drive units and the requirements on the structure of the boat.

In addition to the safety recommendations, the investigators point out to boaters that if there are changes in the voyage plan, enough time must be reserved for getting familiar with the new voyage plan. When this is done, situational awareness is better under control.

An abridged version of the investigation report (deals only with the technical aspects of the incident):

C3/2010M Report (pdf, 5.56 Mt)

The investigation report in its entirety including all the factors considered in the investigation is available only in Finnish.