New Outboard Diesel for Commercial Craft

Durability and safety are essential factors especially for commercial and military vessels. Unfortunately most of the propulsion systems for smaller crafts are initially designed for pleasure craft, says Pim Polesie, Vice President of Cimco Marine Diesel of Sweden.

Combining the inboard reliability with the outboard flexibility and marrying them to a diesel propulsor has been the goal of the marine industry for decades, and Cimco Marine Diesel has now developed a unit that effectively achieves this.

Flexibility, replaceability and maneuverability are often arguments that favor using an outboard propulsion system. Some of the most important advantages to outboard power are the fact that outboards can be tilted up to run in very shallow water and to keep out of water when at rest, says Polesie.

Outboard solutions also deliver a beneficial power-to-weight ratio and are mounted outside the hull which significantly reduces the risk for water intrusion. Also, when moored the engines can be trimmed out of the water which significantly reduces corrosion. They can quickly and easily be replaced with a complete new unit, and this gives the hull more time on water as power unit repairs can be performed elsewhere.
 
The solution’s self-contained belt propulsor unit (S-BPU) eliminates bevel gears and transfer shafts, which can be problematic, by using the latest belt technology. This allows for increased torque transfer to the propeller. It also allows for smaller torpedoes and slimmer submerged modules. This provides less drag and thereby reduces fuel consumption and increases speed compared to gear driven units.

The S-BPU is located on the transom of the vessel and it has a trim tilt system like most outboards do. This is where the commonalities end. An S-BPU is a modular platform that has a horizontal engine configuration in contrast to vertical engine installations. It allows for fully scalable torque transfer capability without affecting the hydrodynamics. 

Using BPU technology makes it fully possible to build a very high powered S-BPU for high-speed crafts. The BPU is a new segment in the marine propulsion industry and not comparable to anything on the market today, says Polesie.

The technology reduces complexity and increases serviceability. All modules are separately serviceable and none of the service parts of the OXE Diesel S-BPU are submerged. The BPU technology contributes to that all shafts are horizontal. Engine, gearbox and propeller shaft are horizontal which reduces the unit vibrations.

The OXE Diesel is the first self-contained belt propulsor unit on the market, says Polesie. The OXE design incorporates:
• Reduced drag
• Increased serviceability
• Less vibrations
• Compliance with SOLAS demands
• Rigid construction
• Reduced fuel consumption

The OXE Diesel S-BPU has been designed to comply with SOLAS demands. The rigid construction withstands great forces and is optimized for commercial use. It allows for long service hours and significantly reduces the fuel consumption compared with other propulsion system due to its slender submerged modules. It is easily reconfigured to fi t the platform it is mounted on due to the changeable gear ratio and the hydraulic gearbox that allows for clockwise and counter clockwise rotation.

The power head is a GM, L4, 2.0-liter turbocharged automotive diesel engine that has been marinized with closed circuit coolant system inspired by modern inboard technology. This provides the unit with a well-proven engine that has been carefully tested over time with reliable technology.

The power-head has been redesigned to arrange all service point in front of the unit so that maintenance and service can be performed on the water. It has been fitted with a dry sump system to allow for rolling in heavy seas, tilting and trimming. The power unit has been mounted on the adaptor plate with four heavy-duty bushings to allow the unit to endure punishing commercial use.

The power from the engine is transferred to the separate stand-alone gearbox via a primary belt system. The primary belt has been designed as the system fuse and adapter. It allows the user to change the gear ratio of the unit to fit various demands and driving styles. By changing the pulleys in the primary belt transition the users can change the gear ratios from 1.3 to 1.47 and 1.66.

The gearbox, mounted separately under the engine is an electro- hydraulically operated system with two multiplate-clutch packages that allows for high torque and power transfer and smooth seamless shifting between neutral, forward and reverse. It has been designed to withstand crash stops and clockwise and counter clockwise rotation so that the unit can replace right and left mounted units.

The use of a hydraulic multiplate-clutch further provides the unit with low-speed capacity through controlled clutch slippage. This effectively allows the unit to seamlessly run from 1 rpm to the end of the rev range. By avoiding minimal running speed units can be used on most platforms and be given search and rescue or patrolling missions where low speed capacity is key as well as interception and transport missions where high speed is required.

The engine meets or exceeds the:
• NATO Single Fuel Directive
• Latest stringent emission standards
• Endurance demands on the commercial market
• Shock absorption capacity of the SOLAS market