VW Marine Diesel

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VW 140-5 TDI Engine

I'll always remember that a sailing instructor (Toddy from Swain Sailing) once told me that the main propulsion system of a big yacht is the engine and not the sails. While I'd very much like like to contradict him, I find that I can't do so; the sails are great but when it comes to docking, manoeuvring in close quarters, getting somewhere when the wind dies down, clawing off a lee shore in weather or anchoring there is nothing that keeps the pulse rate down as much as a faithful and powerful engine.

A marine diesel should be reliable, strong, light and (if one is lucky) quiet and vibration-free. In addition, it should be efficient, run at all angles of heel, easy to maintain and durable plus parts should be readily available at fair prices. That's a pretty long list for any mechanical device to fulfil! The biggest players in the marine diesel market for pleasure sailboats are Volvo, Yanmar, Westerbeke, Universal but VW is making inroads. The engine aboard is the same as the 150-5 (just the electronics have been modified for a lower engine speed) and that is almost the same as that found in the VW Jetta; this means that the parts for the engine can be purchased from most auto parts stores at reasonable prices with good availability.

Hull 68 - Engine The future Zanshin engine. Still all nice and new and shiny, plus note the two alternators (one for 12V and the other for 24V). This picture is part of the story of the Jeanneau Factory Tour.
[46°51'52.71"N 1°1'55.88"W ]
Hull 68 - Engine

One of the great advantages to diesel engines is that they are robust and can continue running even when the electrical system has failed since they use the heat generated during compression to ignite the fuel and don't require a spark from a spark plug to run. I was a bit uncomfortable getting this VW diesel since it uses electronics heavily to generate all those horses in such a small package; but after going through the documentation I see that the engine is designed to fail-safe. While that term has been overused and misunderstood it really means that as parts cease to function they do so in such a way as to keep the engine running. Thus if the electrical systems fail the engine is designed to continue running but will not generate the maximum in horsepower and will degenerate, but continue to run.

In vehicles fuel efficiency is measured in miles-per-gallon or Liters-per-100Km and this is a standardized value based on a given speed in normal conditions. This type of measurement won't work on boats as there are just too many factors that influence the outcome (cruising speed, propeller, hull form, hull growth, wave action, wind, use of sails to name just the major ones). Thus a more typical value used by the technical folk is g/kWh - how many grams of diesel produce how many kilowatt hours and most sailors use fuel consumption per hour. The litres/hour or gallons/hour is a very good number to work with. Unlike in cars, the consumption value won't tell you how far you can get on a tank of gas, but it will tell how long one can run the engine for. Most boats have a published “cruising speed” and if the boat is relatively clean (no growth on the hull) and the propeller pitched correctly it is possible to roughly estimate the range - assuming no help or hindrance from the wind and waves. On Zanshin I have installed an extra fuel tank and that brings my total fuel capacity to 745 litres, the VW 140-5 engine has a consumption of about 7 litres per hour at 1800RPM and doing 7.5knots (according to one of the testing technicians at Flexofold who did the initial testing), this equates to about 1 litre per nautical mile. At this rate of consumption the full tanks would last about 105 hours and the boat would travel 790 nautical miles. This is not a great cruising range for a true blue water ship, but is sufficient for most purposes and I will also carry several spare fuel canisters - another 5 plastic jugs with 100l will augment running time by 14 hours and 107 miles. The number of hours really is the important factor, since with today's efficient satellite weather forecasting systems one usually gets 3 days warning of an impending big storm and that is 72 hours of motoring in order to get out of the dangerous sector.
This range represents doing quite a bit of speed, consumption at 6 knots will go way down; plus it doesn't take the wind into consideration. While motor sailing the sails generate much of the propulsion and the engine isn't loaded as heavily at the same indicated boat speed and thus won't require as much fuel.

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