Bulli have one hand on a drought-breaking George Bass Surfboat Marathon title after winning stage four of the race yesterday.

The convincing victory in the 24-kilometre leg from Narooma to Bermagui followed a similarly emphatic victory in stage three, also yesterday, and put the crew in the box seat heading into today's decisive fifth stage.

Bulli have now won three straight stages after a mechanical failure denied them on day one. Sweep Paul Jones was happy with the convincing nature of the victories.

"We led from start to finish again," Jones said.

"We won by almost four minutes yesterday [Tuesday] and by three minutes and 10 seconds today [Wednesday], so we're hanging around that three-minute mark for the distance.

"We had a massive northerly wind behind us and it's hard to break away from the field when you have a following sea, so the boys did extra well today."

Jones said today's leg, the longest of the seven day race, was crucial to the crew's title hopes.

"It is a make-or-break day," he said.

"A lot of the crews at the front have waited for this day.

"It does sort out a few crews so definitely it's a danger leg for all the crews and especially us because we're in front."

A win would give Bulli a virtually unassailable lead over defending champions Moruya Vikings with two legs remaining.

"We've had three wins versus Moruya's one win," Jones said.

"There's three legs left so they can still win it but if we get a victory tomorrow [Thursday] in the long leg it's going to make it hard for them.

"We're feeling pretty confident but anything can happen in this race."

At 36 kilometres, the row from Bermaghui to Tathra is the longest and most gruelling leg of the seven-day race but Jones said his crew won't change their tactics and are hoping to get to the front early.