Two men lost their lives after poisonous carbon monoxide gas entered the covered cockpit area of a 5.5m sports cruiser, which did not have a CO detector fitted, a Marine Accident Investigation Branch (MAIB) investigation has concluded.

Fumes from the Fletcher 18 GTS’s petrol engine, left running whilst moored at Port Hamble Marina, were funnelled into the cockpit by an inflatable towable ski ring that was suspended from the transom.

The owner of Emma Louise, William Traynor, 44, and his brother-in-law Martin Steventon, 39, both from Slough, died on 11 January 2022 having intended to stay overnight on the boat, moored on a finger pontoon at the River Hamble marina.

The MAIB report found that exhaust gas had built up in the covered cockpit area, shortly after the engine was turned on about 1700, causing them to pass out and die due to CO poisoning.

The likely passage of exhaust gas fumes from the waterline exhaust (a) into the covered cockpit (b & c). CREDIT: MAIB report

The following morning, the owner’s wife became concerned when she was unable to contact her husband, and called the Port Hamble Marina office.

Two marina staff walked to the pontoon and found Emma Louise with its engine idling. They called the emergency services, having been unable to find a pulse on either of the men.

At about 1030, ambulance staff attended and were followed shortly afterwards by officers from both the police and the fire and rescue service. At around 1050, both men were pronounced dead.

Chief Inspector of Marine Accidents, Andrew Moll, said: “The accident onboard Emma Louise serves as another dreadful reminder of the danger posed by carbon monoxide and the speed at which damage to health and collapse can occur. With no CO detector fitted the two men were unaware of the danger and were tragically overcome within minutes of starting the cruiser’s engine.

“CO is colourless, tasteless and odourless and difficult for people to detect. It is essential that CO alarms are fitted in areas where carbon monoxide can accumulate such as the cabins and cockpits of motor cruisers.

“Never ignore the smell of exhaust fumes in any enclosed space. Boat users are once again reminded of the three simple but life saving measures that will help you to stay CO safe: install and maintain equipment properly; fit CO alarms and test them regularly; and always ensure there is adequate ventilation in the cabin.”

You can read the full report and download a safety flyer detailing the lessons learned and advice for dealing with carbon monoxide on a boat from the MAIB website.

A Boat Safety Scheme (BSS) spokesman said: “While the Hamble and most other coastal marinas are not Boat Safety Scheme implemented moorings and berths, our advice is still very useful for all boat owners.

“For the majority of inland waterways, navigation and harbour authorities have implemented the BSS requirements and boats with cabins are obliged to have suitable working CO alarms.

“Unfortunately, our examiners continue to find that around 9% of boats do not meet this requirement. And the terrible events on Emma Louse, Diversion, Love for Lydia, Vasquez, Arniston and others indicate how absolutely vital it is to have a working CO alarm, and not just to get a BSS Certificate.

“Our information on dealing with the risks of Carbon Monoxide poisoning is available for all at boatsafetyscheme.org“