PPSP managing director Captain Robert Buck and the boat's builder, Mal Hart of Mornington-based Hart Marine, watched with satisfaction as the $3million-plus Akuna IV was lowered into the water in Mornington harbour about 9am.

Six hours earlier, in darkness and fog, the orange and black Akuna left Hart Marine in Yuilles Road on a low-loader, accompanied by VicRoads officers in two cars and power company workers.

It took about 20 minutes to manoeuvre out of the Hart Marine yard and then it was plain sailing, so to speak.

In the well-planned operation, power lines were lifted to about six metres high as the low-loader moved down Main Street to the football ground, where it turned left into Cromwell Street and travelled down the ring road, over Barkly Street and to Queen Street for a tricky left turn back into Main Street and then down to the harbour.

The journey took about 40 minutes.

At the harbour, Akuna (Aboriginal for "flowing water") was jacked up and fitted with stern fins, propellers, aerials and other items before being lowered into the water. The pilot boat will be based at Martha Cove marina for 10 days of sea trials before being commissioned to carry pilots to and from ships using Port Phillip.

The 18-metre long Akuna will be joined by a slightly smaller sister boat, the 14.3-metre long Ranger III, in about a week. Ranger will be based in Western Port.

The two pilot boats were built by Mal Hart and a team of 40 over the past 12 months.

Akuna is six metres wide, has a draught of 1.6 metres and is powered by twin 800-horsepower Cummins diesels with a top speed of 30 knots.

Mr Hart said the boat had the latest in low-emission, low-noise, low-vibration motors.

"It's so 'green' we have been asked to tender for the [environmentally sensitive] Gorgon gas project in WA," he said.

Akuna is based on a French design but adapted for wild conditions often experienced at The Heads.