Dive Boat - NADZAB


I have owned a number of dive boats over the years. I initially started with a very small zodiac inflatable called a ZED powered by a Johnson 15 HP outboard (this was back in 1981). It was very small and only suited to two divers with minimal equipment, but it was very useable and could be transported and inflated anywhere. I then upgraded to a larger inflatable zodiac called a Futura Mark 2 powered by a Johnson 25 HP outboard. In between the disposal of this boat and the purchase of a larger zodiac Futura Mark 3 powered by a Evinrude 45 HP, I used a Cruisecraft Ranger 18 powered by a Mercury 115 2 stroke outboard. Most recently, before the purchase of my latest dive boat, I was using a Quintrex Sea Raider aluminium boat powered by a Yamaha 115 - 2 stroke outboard.

I have always liked the zodiac inflatable range of boats and believe they make excellent diving platforms for close in-shore diving operations. They are light, suck onto the water well, and with their flat bottoms provide exceptional stability. The downside is that they are a wet boat! If conditions become rough you will always get wet!

At the bottom of this page are some pictures of the dive boat we are currently using. It was purchased in September 2002 to replace the Quintrex Sea Raider powered by a Yamaha 115 - 2 stroke engine. This boat is a plate boat (5 mm) manufactured by Trailcraft in Western Australia. The overall length is 6 m and the beam is 2.35 m. It's powered by a Bombardier 140 - 4 stroke engine and has a Johnson 15 HP (2 stroke) auxiliary. Instruments include a Navman Fuel Management Computer and a Garmin 188-C GPS / sounder chart plotter in addition to standard gauges, radios, EPIRB and safety equipment. Fuel tank capacity is a HUGE 250 litres! I also have an additional Navman digital depth meter fitted.

Trailcraft Boat Evaluation

The Trailcraft 5.8 sports-cab "plate" boat is absolutely fantastic. Very solid (5 mm sides and decking) and exceptionally well designed and constructed. Paint work is very good. A few welds are a little sloppy, but this is on the inside only, and in out of the way places like under the bulkhead. The two solid swivel seats are comfortable and have storage available inside the pedicel by opening the seat and folding it forward. The seats do not lock in one position, which can be a hassle (they can swing). The glass windscreen is excellent – no more scratches! Inside space is ample for 4 divers and equipment. 2 bunks (well sort of bunk-like) are suitable for sleeping two adults and the higher than normal cabin roof provides greater head space. Walk-around deck with anti-slip paint is a great idea to facilitate access to the bow and the very deep anchor well – no more bouncing anchor in a swell! The high bow and side rails are also very solid and extend beyond the edge of the boat. The bow rail and snout in front of the anchor well is ideal for deploying and retrieving the anchor.

Best of all is the walk through transom door and dive ladder. This is the BEST dive ladder I have used. A fully kitted diver in a drysuit can leave and enter the boat wearing weight belt and fins using the ladder. The transom door would have to be the best aspect of the boat considering it is used solely for SCUBA diving. The door is solid and can be locked in the open or closed position. A large water proof box is also located at the stern which houses the 2 dry-cell batteries and other odds and ends that you don’t want to get wet. The box doubles as a seat.

The boat’s stability at rest is very good, but not as good as a Quintrex Offshore. The main difference here lies in the dead-rise angle which is a higher angle in the Trailcraft and a lower angle in the Quintrex. Still I have no complaints on the stability. As you know, divers usually fill their boats with water, but this boat has a self draining deck, so no water or other unwanted oddments fall into the hull. Two large self drainer hatches can be opened at the stern which allow any water accumulated on the deck to flow out of the boat. Another plus to this boat is the rocket launcher which can be folded down in about 3 minutes for storage in a garage. The launcher is ideal to position floodlights, Garmin GPS pods, antennas and the dive flag. Lastly, the fuel tank has a capacity of 250 litres!


The performance of the boat is excellent, especially in a rough sea. I have taken the boat out into 30 knot winds and a 3 meter breaking sea without any major hassle (not that I would recommend this). The craft handles the seas very well and did not nose dive down swells. Of importance considering the aluminium construction is the ride, which is almost as comfortable as a glass boat. There is NO bang bang bang that aluminium boats are renown for. Just a swish as the water is pushed to the side. Occasionally there is thump, but it is not bone jarring as in most non-plate aluminium boat designs (Quintrex). The deep vee hull pushes most of the water to the side and very little water goes over the bow or over the top of the boat. As such it is a very dry boat.

The boat is a heavy boat, however compares favourably against the Quintrex Offshore dry weight. The 5.8 m trailcraft is a little lighter than an equivalent sized glass boat. You should remember that the boat with engine, fuel and accessories is heavy and as such, a good towing vehicle is recommended. I use a Landcruiser with a 4.2 naturally aspirated diesel engine – a turbo would help on the hills. I would think a petrol 4.5 L Landcruiser would pull this boat with ease with stacks of power to spare. On average I can tow the boat safety between 90 and 100 km/h on a flat road.

Bombardier Outboard 140-4 Stroke Engine

I thoroughly researched the type of engine that would power my boat. Initially was going to purchase a Yamaha 115 4 stroke, however decided on a larger horse power and bought a Bombardier 140 HP 4 stroke. I am not regretting my decision. This engine is identical to the Suzuki DF140 4 stroke (minus colour, name badge and engine cover) that has just been released in Australia and has been very successful in the USA for the past 2 years winning several awards. The engine is lighter than the Yamaha 115 4 stroke and fairs favourably to the weight of a two-stroke. Warranty on the bombardier 140-4 is 3 years.

Performance, Power, reliability and Environmental Benefits

The engine starts first time every time, just like a car engine. It is super quiet and has absolutely no smoke or petrol fumes. Idling the engine, folks ask me if it is turned on! At 4500 RPM the noise replicates a dull roar, but nowhere near as loud as my previous Yamaha 115-2 stroke. Power to weight ratio is excellent and top RPM is 6200 to 6400 depending on engine trim. On take off it is marginally slower than a two stroke, however you become used to this very quickly. The 140 HP is more power than I need for this sized boat - which the way I like it, so if I need extra power crossing a bar I will always have it available. Remember also that we are carrying dive gear which is heavy.

One aspect requiring some time getting used to was when docking onto a pier or jetty. You have to remember to put the engine in reverse a little sooner than you would with a 2 stroke engine; this is because the power is more lower end on a 4 stroke engine. The other option is apply additional reverse thrust. It just takes a little extra time to get used to.

Fuel Consumption

The fuel consumption is outstanding considering the horse power, size and weight of the boat even with the addition of diving equipment. I have a Navman fuel management gauge fitted so I can manage my fuel consumption (great gauge by the way and strongly recommended). At 1500 RPM the engine uses 7 Litres/hour, at 4200 RPM fuel usage is 23 L/hour, at 4500 RPM usage is 25 L/hour, at 4500 RPM usage is 25 L/hour, at 5000 RPM usage is 30 L/hour, at 5500 RPM usage is 36 L/hour and at 6200 RPM engine fuel usage is 45 L/hour. These calculations were on a good day with a little slop. If I trimmed the engine right out, the fuel consumption would be a little bit better. And remember no additional 2 stroke oil to mix or buy. The cost of running the engine is the price at the pump!

Environmental Benefits and User Comfort

The best benefit I believe with this engine, other than no fumes, no smoke and good fuel economy, is that it is environmentally friendly with no, or very little fuel and oil discharge to the water. I believe that if the technology is available (and it is) then it is every boat operator's responsibility to minimise outboard motor oil and fuel pollution. In my opinion, the 4 stroke wins every time in comparison to a 2 stroke. I will never purchase another 2 stroke outboard.

My opinion - for what it's worth

The Trailcraft and bombardier are the best combination I have ever used. I would definitely purchase both again.

What's in the Name NADZAB?

Why call the boat NADZAB? Nadzab is the name given to a small airfield near Lae, Papua New Guinea. The airfield was the major stepping off point for the allied air advance during the Second World War. Today jets land at Nadzab field and this airfield is one of the central hubs for visiting divers to PNG. I think PNG has some of the best diving on Earth, hence the name and the connection to a dive boat.

BELOW: A few photographs taken during a recent diving trip at Eaglehawk Bay at Tasman Peninsula. Towing vehicle is a Toyota Landcruiser 4.2 naturally aspirated diesel four wheel drive. Note the boat has an excellent ladder, boarding transom and rear door.


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