| Vessel Make: | Mariner 3400 |
|---|---|
| Old Engines: | Iveco 8061 |
| New Engines: | FPT NEF 280 |
| New Engine Rating: | 280HP @ 2800rpm |
| Cruise Speed: | 18kn @ 1800rpm |
| Max Speed: | 26 knots |
Mariner 3400 โ Former Western Australian Police Force Vessel Protector
Some projects come full circle, and this one has been nearly 40 years in the making.
Originally delivered to the Western Australian Police Force in 1986 as PV Protector, this Mariner 3400 isn’t just another repower. It has a long-standing history with THT, with our team supplying the original Iveco 8061 marine engines when the vessel was first commissioned.
It also holds a special place in our company’s history. This was the very first vessel that our General Manager, Andrew Hare, sea-trialed as an apprentice. Nearly four decades later, Andrew was back onboard, this time with his son, Josh, to complete a new repower.
The Mariner 3400 is a fantastic vessel. At 34 feet in length, it offers a wide beam, generous internal space, and an exceptionally solid hull built for survey work. Like many Mariner vessels, it has stood the test of time.
However, one of the biggest challenges with these boats is the engine room. Despite the spacious hull, the engine room is extremely tight, leaving very few engine options that physically fit while still delivering the desired performance.
This is where FPT Marine engines excel.
Thanks to their compact design, the FPT range provides multiple repower options where many other engines simply won’t fit.
The Solution
For this project, THT installed:
- 2 ร FPT NEF 280 mechanical marine engines
- 280 HP at 2,800 RPM
- 6.7-litre turbocharged engines
- Mechanical fuel injection (non-common rail)
Although common rail technology offers many advantages, every repower is selected based on the customer’s objectives. In this case, the mechanical NEF 280 provided the ideal horsepower while perfectly matching the existing driveline.
The engines were paired with the vessel’s original MG506A gearboxes, which were retained, rebuilt and reused.
These gearboxes feature a near-coaxial design, allowing the crankshaft centreline and gearbox centreline to remain aligned before the down angle. Reusing them meant the existing shafts and propellers could also be retained, making the overall package an ideal match.
New propeller shafts of 2205 grade, 1.75″ diameter were installed and the existing 3 blade propellers were reused.
Even with the larger displacement engines installed, clearances remained incredibly tight, with approximately 10 mm above and 10 mm below each engine.
It’s another example of why selecting the right engine is about much more than horsepower alone. Understanding dimensions, gearbox compatibility and driveline geometry is essential for a successful repower.
Modernising the Controls
The repower wasn’t limited to the engines.
THT also installed a new Flexball throttle control system, bringing the vessel’s controls up to modern standards.
The lower helm station was removed, with the flybridge becoming the primary operating position.
To make docking even easier, the vessel was fitted with a Flexball Wireless Remote Control (WRC). The system allows the skipper to control:
- Engine throttle and gear selection
- Bow thruster
- Optional stern thruster integration
- Anchor winch (optional)
The result is significantly easier and safer manoeuvring, particularly when operating short-handed.
Performance Results
Built originally for survey work, the Mariner features an exceptionally strong and capable hull that responds well to increased horsepower.
With:
- Twin FPT NEF 280 engines
- MG506A 1.5:1 gearboxes
- 1.75″ 2205 Grade Shafts
- Three-blade propellers
- Approximate displacement of 8 tonnes
โฆthe results were impressive.
Cruise Speed
- 18 knots at 1,800 RPM
Maximum Speed
- 26 knots @ 2850rpm
Considering the vessel is powered by two 280 HP mechanical engines, these figures demonstrate just how efficiently the package performs.
Why Older Boats Are Worth Repowering
We’re seeing more owners choosing to repower quality Australian-built boats from the 1980s and 1990s rather than replace them.
Boats like the Mariner, Randell, Precision and Northshore were built with incredibly strong hulls that still have decades of life left in them.
With the right engine package, they can be transformed into modern, reliable and economical vessels while retaining everything owners already love about the boat.
No matter what engines are currently installed, THT can provide an FPT Marine repower solution tailored to your vessel, delivering modern performance without compromising the boat’s proven foundations.
Thinking about repowering your vessel? Talk to the team at THT. Choosing the right engine isn’t just about horsepowerโit’s about selecting a package that fits your hull, gearbox, driveline and boating goals.
