This has prompted calls for more people to be vigilant when taking their boats out on the water.

A mother and her three-year-old son were seriously injured and another two family members were injured after their boat was engulfed in flames on the Murray River.

The family of five were travelling on a speed boat near Moama, on the NSW and Victorian border on Saturday afternoon, about 2.45pm after leaving the Echuca East boat ramp.

When the family neared Goldborough Road they encountered mechanical issues and when the engine restarted it exploded, according to police.

Emergency services attended and the family were rescued and taken to Echuca Hospital.

A 43-year-old woman was airlifted to Alfred Hospital, in Melbourne, and her three-year-old son was airlifted to the Royal Children's Hospital, Melbourne, after both sustaining burns to their legs.

They remain in a serious but stable condition.

A 50-year-old man and a 19-year-old man received minor burns and remain in Echuca Hospital, while a 12-year-old boy escaped injury.

The boat was totally destroyed and an investigation has commenced surrounding the circumstances that led to the incident.

Wagga Marine owner Craig Harris said people should get their boat checked by a qualified boat mechanic prior to taking their boat out for the start of the season.

"They should get their boat checked every 100 hours or every 12 months," he said.

"Any boat that has a battery has to have a fire extinguisher, by rules and regulations from NSW Maritime.

"But, the positioning of the fire extinguisher is a big thing and should not be positioned near where the boat can catch fire."

Mr Harris is a former fireman, with more than 16 years under his belt.

He said boat sales have taken a dive this year and people are choosing to utilise their older boats, which have the potential for problems to arise.

"Boat sales have been down this year ... there's less services because of the economic climate and climate itself," Mr Harris said.

"People also need to do their own fuel checks, but if there's a leakage - don't try and start it.

"The biggest thing is being vigilant; if there's any smell of fuel, take it to someone who can check it out. Adults can swim, kids can't."

Mr Harris advised people should undertake a first aid course.

This comes less than a month since two adults and two children were injured after their boat exploded at Lake Albert on November 20.

It was later revealed by Riverina Police District Detective Acting Inspector Phil Maligan that the family had bought the vessel second-hand and it was their first time taking it out.