There were also no communication devices on the boat and it was likely neither were wearing lifejackets, Dr Bain said.
Phone calls and texts messages proved unsuccessful for family trying to contact the two men when they did not return.
Mr Pooley failed to turn up to a job interview two days after the men had set off.
Police were alerted after Mr Roberts' dog returned home and two cars and a boat trailer belonging to the men remained parked at Jones Landing.
Both men were wearing heavy clothing and had been drinking and it was not clear if the boat was equipped with lifejackets, or if the men were wearing them.
Lake Arapuni is heavily infested with weed and regarded as hazardous to boaties.
Sonar searches failed to find the boat and it was likely it had sunk after becoming caught in the thick weed, Dr Bain said.
Blood alcohol tests had showed high levels of alcohol in the men's bodies.
"Drinking was not the wisest thing to do, particularly in a small boat," Dr Bain said.
"These men should have told their families and friends where they were going and when they were expected back."
Mr Bain said it was necessary to highlight these factors to prevent others making the same mistakes and hopefully save a life.
The matters raised by the court were "simply common sense for boating which should be brought to the attention of others as to the risks they run when they don't take simple safety precautions," he said.
Mr Pooley's mother, Helen Pooley, said the findings were truthful and had now brought closure for the family.
"That's all we really wanted, we can now go forward," she said.
"It's a message to anyone who goes out in a boat - don't drink, and for god sakes let someone know where you are going and when you are coming back."