30 years of engines and propulsion
The past 30 years have seen dramatic changes in marine engines and their associated propulsion systems.
30 years ago there were still dedicated marine diesels such as the Gardner and Lister engines being produced but in 1987 the writing was on the wall for these robust slow revving engines and a new order of automotive diesels was taking over. The market for marine diesels is relatively small compared with overall engine production and even those Gardner and Lister units were developed from engines designed for other purposes.
The increasing sophistication of diesel engines designed to meet more stringent emission standards and the demand for better fuel economy meant that the development costs were high and it was only through mass production techniques that the costs could be contained. So almost without exception all modern marine diesels are based on engines developed originally for cars, trucks, generators and agricultural purposes. The one exception is the Seatek high performance diesel made in Italy which was developed specifically as a very high performance unit for powerboat racing and fast patrol boats. This was one of the first marine diesels to exceed the 100hp per litre benchmark.
That benchmark power figure has now become the norm for many engine builders and the past few years have seen an avalanche of engine manufacturers moving into the high performance market. The high performance combined with lighter weight is a spin-off from the need to improve efficiency and reduce fuel consumption. 30 years ago the performance engine in the MTU range was the 396 V-12 diesel but with the introduction of the 2000 and 4000 ranges of high performance diesels MTU has established an enviable position in the performance sector almost halving the size of the engines for the same power.
Rivals MAN have not been far behind but have focussed more on smaller horsepower engines. American rival Caterpillar was renowned for what many considered to be its rugged but agricultural larger diesel engines but they have now caught up to the point where they are challenging the two German manufacturers. It is the same with Cummins and there are two European engine manufacturers who are hoping to challenge in this competitive market. French company Moteurs Baudouin was renowned for its rugged slow running diesels but is now offering a powerful V-12 diesel aimed at the performance sector.
Italian engine builder FPT which is part of the mighty Fiat Group has steadily expanded its range of performance engines over the years and watch out here for a major new engine development to be announced soon. FPT like nearly every engine manufacturer has switched its engines to the common rail fuel system which means that the engine is now electronically controlled. This has helped to boost power outputs and reduced the emissions but it also means that modern engines will not run without an electrical supply which some may consider a retrograde step in terms of ultimate reliability.
Ironically Seatek who triggered the high performance engine development has not switched to common rail systems but it must be only a matter of time before they do. One of the keys to the Seatek performance was the high speed of the engine and in a significant development for diesels we are now seeing most performance engine operating in the speed range of 2500 to 3000rpm versus the significantly slower speeds of 30 years ago.
Diesel outboard motors have always had an attraction to smaller workboat operators because of the ready availability and safety of the fuel so when the small Yanmar diesel outboards were taken off the market because they could not meet modern emission standards there was a considerable gap in the market. This gap is now being filled by a host of new names on the marine engine market. One of the first was the Neander Shark 50hp unit which is being marketed by Yanmar. This was followed by 200hp Oxe outboard developed by Cimco in Sweden and based around a 2 litre GMC automotive diesel connected by a belt drive system. Waiting in the wings is the innovative 300hp Cox outboard, a sign of how the diesel outboard market has come of age in the past 30 years.
Transmitting the power from these high performance diesel engines to the water has been an equal challenge for the propulsion industry. 30 years ago the options were mainly conventional shaft and propeller systems, stern dives and water jets. The surface drive was in its infancy and finding its way onto fast patrol boats with the Arneson Drive leading the way. There were various alternatives such as the Trimax but the patent of the Arneson prevented too much innovation. When that patent expired a host of new surface drives appeared on the market but the surface drive market is still a small proportion compared with the overall market.
In the workboat and ferry sectors the water jet was gaining respectability led by the demand for large water jets from the new generation of big vehicle-carrying fast ferries. Water jet propulsion has now taken over to a large degree from the stern drive as the propulsion system for smaller workboats and RIBs. The stern drive suffered because the earlier drives had difficulty in handling the high torque of the diesel engines although more modern drives are better equipped in this respect with the Konrad Drive perhaps considered to be leading the way for diesel engined boats.
The IPS Drive from Volvo Penta was the first of the pod drives and while it was a big hit in the leisure sector it has not really caught on in the workboat and patrol sectors. There has been a selection of other pod drives from manufacturers such as ZF and Mercury with Reintjes a late comer in this sector with its innovative pod drive with propellers at each end of the pod. Rolls Royce also has a pod drive made from composites.
Pod drives led to the wonders of joystick control that brought a whole new meaning to boat handling and now joysticks are available for stern drives and even for conventional shafts and propellers provided they are combined with bow and stern thrusters. The workboat sector demands reliability and so the tried and tested solutions are usually the system of choice for many operators.
Where will it all end? Well we are seeing the changes coming already with hybrid and full electric drive systems now edging into the workboat sector. Battery powered craft could feature in a new generation of harbour craft where charging points can be arranged easily but for offshore and remote areas hybrids are probably the way to go offering the possibility of operating the vessel at lower speeds by just running the generators. Gas fuelled diesel engines are a regular feature in shipping these days and MTU will be operating gas engines on a ferry soon. Tugs may switch to gas engines but there does not appear to be any sign of this being a feature of small workboat engines. It is the quest to meet reduced emission standards that is now governing the engine market whereas 30 years ago it was performance that was the key to development.
By Dag Pike
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