The 83-year-old Lady Derwentwater, which has been owned and operated by The Keswick Launch Company since 1935, now sports a pair of naturally aspirated M92B engines.

Throughout the year, Lady Derwentwater carries up to 90 passengers at a time on cruises around the 4km long lake in the heart of the Lake District National Park. The 17-metre long boat is carvel-built; a traditional method of constructing wooden boats by fixing planks to a frame so that the planks butt up against each other, edge to edge, gaining support from the frame and forming a smooth hull. The new engines are coupled to Newage PRM 500 D2 gearboxes and provide Lady Derwentwater with a cruising speed of 10 knots.

The new engines replaced the predecessor of the M92B, the M92, which had given Lady Derwentwater years of sterling, trouble-free service. However, the M92B is 3dBA quieter than the M92 and six percent more fuel efficient. The engine has up to 12 percent more low speed torque and 26 percent more torque back-up than the M92. The direct injection, four-cylinder, 4.4-litre engine also boasts extended service intervals with a 500-hour oil change regime. It is based on the high-durability Perkins 1100 Series engine and develops its maximum power at a comfortable and low stressed 2,400rpm.

From the passengers’ standpoint, an important factor in its favour is that the M92B’s smoke levels are barely visible to the naked eye. From The Keswick Launch Company’s perspective, the fact that it is dimensionally very similar to the boat’s original M92 engines meant that repowering was quick and easy without the need to make any structural alterations to the boat or even change the engine mounts.

The engines installed in Lady Derwentwater are standard M92B specification. This includes fresh water heat exchanger cooling, with gear-driven, self-priming raw water and fresh water pumps. The engine has a fresh water-cooled exhaust manifold, intake manifold and heat exchanger, and a high-inclination engine sump with a sump drain pump. It also incorporates an inverted spin-on element lubrication oil filter, a transmission oil cooler, totally enclosed engine breather and a high-mounted single element fuel filter.

When it was introduced in 2005, the M92B was a trailblazer. At that time it was the first marine propulsion engine in the world that was clean enough to be certified as complying with CCNR [Central Commission for Navigation on the Rhine] Stage Two requirements, which did not even come into force for another two years.

The engines for Lady Derwentwater were supplied by Cannock-based Finning (UK), the Perkins distributor for England, Wales and Ireland. Parts and service support are available only through the Perkins distribution network that today numbers 132 distributors in 184 countries. Full details of the M92B and the other engines in the current Perkins Marine Power range, including contact details for the distributor network, are available on www.perkins-sabre.com.