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post #1 of Old 06-10-2002 Thread Starter
Mark Matthews
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Diesel Maintenance

I am purchasing a 32-foot Endeavour that has a stock 20-horsepower, raw-water-cooled Yanmar diesel. What are the top five upgrades you would recommend to make servicing the engine easier and its operation more efficient?

Mark Matthews responds:
Thanks for the question. With clean fuel, clean air, and good compression, a diesel engine should last for years and years. Here are some general thoughts about maintaining diesel engines.

The first thing I would recommend is simple, but it's an item that often gets overlooked: install a bright light in the engine compartment. Being able to see fuel or oil leaks, chafing fuel lines, throttle cables, or wires is the first step in preventing major engine disasters. Many marine engines can become salty, dank-smelling things, and a little Martha Stewart ambience in the engine room can go along way toward illuminating what needs to be maintained before the engine conks to a halt in the middle of a shipping lane.

If youíre dealing with a rusty, paint-peeling beast, clean up the engine with some degreaser and repaint the engine. This isn't just a good maintenance practice, it's also a great way to get familiar with the engine. And clean engines are more likely to be functional engines.

Since you ask about pertinent upgrades, and your Yanmar is raw-water-cooled, you might consider changing to a freshwater cooling system, or at least affecting an arrangement that will allow you to flush the engine out with freshwater from time to time. Because the engine takes water from the outside to cool itself, small twigs, sticks, marine life, and other flotsam can lodge in the strainer, clogging it, and cause the engine to overheat. But the buildup of scale is really the big concern. Ocean water, which is corrosive by nature, will build up mineral deposits over time inside the water jackets and other water passages that are crucial to keeping the engine from overheating. And another big problem has to do with regulating the engine temperature. As the water temperature varies, so does its effectiveness to cool the engine. And many raw-water-cooled engines lack a way of governing the flow of water. Those that do have such devices are prone to fouling because of scale and other contaminants.

If you donít already have one, the third upgrade Iíd recommend is an engine hour meter. Hopefully you already have oil pressure and temperature gauges that are connected to alarms. An engine hour meter takes the guesswork out of oil and oil filter changes, as well as fuel filter changes, which should help foster an assiduous maintenance outlook. Also, get a maintenance log and be diligent about recording the dates when you change the oil and filters.

If you have to be a yogi master to get to your filters, consider rerouting the fuel line and filters to take some of the negative stimulus out of this procedure as well. Anything that is easier to do is more likely to be done when it comes to engine maintenance.

Also, take a good, honest look at the fuel tank, and better yet, take a sample from the bottom of it. If youíre dealing with a boat that has something of a mysterious past, consider having the fuel tank professionally cleaned. If youíre dealing with a large tank that has baffles, that may not get all the particles out. A bad batch of diesel, or diesel that has been sitting for a long time can introduce sediment in the fuel lines (leading to clogging) and condensation can also accumulate in half-filled tanks. In a rough sea, the sediment can become dispersed throughout the fuel and cause the engine to sputter to a stop.

If the tank exhibits signs of corrosion or has pinhole leaks, itís time to replace it. Depending on the access, this can be a labor-intensive, and/or expensive proposition, but itís either doing that or you'll face rebuilding the engine later on, and that carries an even heftier price tag.

My fifth recommendation is really more of an amalgam of recommendations. Proper valve adjustment, engine alignment, belt tension, and clean air filters, as well as fuel injectors that are serviced periodically will all contribute to keeping your engine purring. Before you start the engine, check the oil level, transmission level, and fuel filter sight glasses, and after the engine is started, make sure water is coming out the exhaust port. Get into good habits early and youíll circumvent a lot of headaches later. Good luck.

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