Hobart boat deaths an avoidable tragedy

All boats with enclosed cabins and petrol motors should have carbon monoxide detectors after the "completely avoidable" death of two mates in Hobart, a coroner says.

Gregory John Burling, 58, and Brian Owen Daley, 56, were found dead in a boat moored in Prince of Wales Bay in January 2016 after inhaling exhaust fumes while sleeping.

Coroner Simon Cooper says they suffered carbon monoxide poisoning caused by a "poorly installed and maintained" petrol-driven generator.

He described the deaths as a tragic accident.

"Both deaths were entirely avoidable and were due to ... the absence of any device to warn as to the presence of carbon monoxide in the cabin," according to Mr Cooper's findings published on Thursday.

"The generator should never have been installed where it was."

The generator had a home-constructed exhaust extension that allowed fumes to enter the cabin.

The pair were on a sailing trip down Tasmania's east coast with friend Barry Lowe and his young daughter.

The father and child left the boat the day before the tragedy, on January 9, after she started having seizures and was airlifted to hospital.

High levels of carbon monoxide were later found in her blood.

Mr Lowe returned to the boat the next morning to find his friends dead.

Mr Cooper also recommended petrol-driven generators not be used in confined spaces and only in line with manufacturer guidelines.