A jury has expressed grave concerns over the regulations governing ocean-going yachts after it cleared the director of a sailing management company of the manslaughter of four sailors who died when the Cheeki Rafiki sank mid-Atlantic.

Relatives of the four, all experienced sailors, wept when Douglas Innes was found not guilty of the men’s manslaughter.

Innes, from Southampton, and the company Stormforce Coaching are to be sentenced next month after being convicted at a previous trial of failing to operate the yacht in a safe manner contrary to the Merchant Shipping Act.

Unusually, after clearing Innes, the jury on Wednesday handed a note to the judge, Nigel Teare, revealing concerns over the certification and testing of yachts.

The note said: “We are deeply concerned by the evidence we have heard about the regulations involved in this case. Pleasure and commercial regulations need to be clarified.”

Winchester crown court was told there was confusion over the regulations and certain inspections did not involve structural surveys and could be carried out by people who were not qualified surveyors.

The chief executive of the Maritime and Coastguard Agency, Sir Alan Massey, said it would look at the regulations questioned by jurors.

He said: “The sea can be an extremely hostile place and you must make sure your vessel is properly maintained. [The jury] made recommendations and we will follow them up.

“If we need to review or amend any regulations we will. Our thoughts are with the families; it is fundamentally their feelings that matter in this case.”

What is known of the last days and hours of Cheeki Rafiki and its crew has been set out during two trials at Winchester crown court and in a marine accident investigation branch (MAIB) report.

The yacht – named after a character in the Lion King – took part in a cross-Atlantic ocean race in December 2013 and competed in Antigua Sailing Week in April 2014.

It set sail for its base port of Southampton on 4 May 2014. On board were skipper Andrew Bridge, 22, from Farnham in Surrey, and mate James Male, 23, of Southampton. Both were working for Stormforce Coaching.

The crew members were amateur sailors Steve Warren, 52, and Paul Goslin, 56, friends from Somerset for whom the voyage was a dream trip.

Their crossing was due to take 30 days. At first progress was hampered by light winds and, according to the MAIB report, Stormforce Coaching sent the vessel an email on 6 May saying: “Go north, do not pass go, go north, do not collect £200, go north.”

Cheeki Rafiki, which capsized in the mid-Atlantic killing four crew members. Photograph: Royal Yachting Association/PA

The wind and waves picked up. On 14 May, Bridge emailed base that the vessel had “just hit a big wave hard”. The next day, the yacht emailed: “We have been taking on a lot of water yesterday and today. Today seems worse.” By now the boat was being struck by waves of almost five metres high and force seven winds. It was 1,000 miles off the US coast.

At about 4am on 16 May, an alert transmitted by the personal locator beacon of Cheeki Rafiki’s skipper triggered the US search and rescue operation. The next day, a container ship located the upturned hull of a small boat, believed to be Cheeki Rafiki. The search was called off.

After pressure from the missing men’s families, the British government intervened and formally asked the US to continue looking.

On 23 May, a navy helicopter found an upturned hull, identified it as Cheeki Rafiki and confirmed that its life raft was still on board in its usual stowage position. The men’s bodies were not found and the hull was not recovered.

On what might have caused the vessel to sink, the MAIB report says: “A combined effect of previous groundings and subsequent repairs to its keel and matrix had possibly weakened the vessel’s structure where the keel was attached to the hull. It is also possible that one or more keel bolts had deteriorated.”

During the trials, the prosecution went further. It alleged the sailors died after Innes, 43, had neglected the “unsafe” vessel for several years by failing to maintain it.

It was claimed that when Cheeki Rafiki began taking on water, Innes was in a pub in the UK. The crew emailed Innes but instead of alerting the coastguard at once, he is said to have carried on drinking and even went to another bar.

Later he returned home, called the coastguard but, according to the prosecution, did not say that the situation was urgent.

Innes said initially the skipper was simply asking for advice and he did not see it as a big problem. He told the court that later when he realised the seriousness of the situation he did go home so he could “give it 100%”.

He insisted Cheeki Rafiki had been regularly maintained and inspected with no evidence of damage to the keel. He said he had not tried to cut costs by ordering the vessel further north.

At the end of the first trial, he was found guilty of failing to ensure the safety of Cheeki Rafiki but the jury failed to reach verdicts on the manslaughter charges. A retrial was ordered on those charges.

• This article was amended on 27 April 2018. An earlier version misnamed the judge, Nigel Teare, as Douglas Field.

