America's Definitive Marine Engine Magazine
The contemporary marine engine is an undisputed modern marvel combining strong performance and enviable fuel economy with long life. Even so, preventive maintenance is required to prevent early retirement. With that in mind here are eight simple rules for maintaining a healthy inboard, outboard or stern drive.
That's because spent well-worn oil is acidic, abrasive and thick with sticky varnish. Procrastinating, or outright ignoring, a scheduled oil change means all the while dreck etches bearings and journals and cylinder walls pitted. Worse yet, sticky oil glues oil control rings in their piston grooves, causing an otherwise healthy engine to shamelessly burn oil. Tip: A suction pump draws old lubricant out of the crankcase and minimizes mess. Also, oil that's been drained shortly after engine shutdown retains impurities in suspension, so they leave the oil pan instead of settling in the sump.
Tied off dockside for weeks on end, ambient air enters the combustion chamber through open exhaust ports. Condensation drips on the exposed cylinder walls causing rust and pitting that abrades the compression rings the next time the engine is started. During winter lay-up we fog engines. But dormant periods, says as short as two weeks, could also benefit from an abbreviated burst of fogging oil down the air intake. Do it immediately before clicking off the key. That way oil vapors coat the cylinder walls and valve stems, protecting them from corrosion.
Damaged, out of balance propeller blades vibrate the wheel, sending a shudder up and down the entire drive train. Driveshafts have been known to fracture from this kind of a beating. Usually you can feel the reverberation in the soles of your feet. But even when all appears well it's still a good idea to regularly eyeball blades for nicks, and more importantly, for missing chunks of metal. Take heart. Even seriously mangled wheels can often be repaired.
Know that operating costs are measured by more variables than just fuel consumption. Incessantly running at wide-open throttle prematurely wears piston rings and crankshaft bearings. In sharp contrast, throttling back to cruising speed pays big dividends. The ride is more comfortable and the loafing engine logs significantly more hours before it's time to put a wrench on it. Depending on the engine, mileage is also usually better.
Scrupulous scrubbed fuel means less wear and tear on carburetors and fuel injectors. Conversely, dirty fuel is like liquid sandpaper, with micron- sized particulate matter eroding critical dimensions. Consider plumbing a dual filter setup. This means two filters in series, the first one pulls out 30 micron or larger particles, the next one in line ten micron-sized particle. Obvious a fuel/water separator is an important part of the package. Tip: In areas where fuel quality is third world, pre-filter through a screened funnel right at the fuel dock to keep stones and pebbles out of the tank.
According to Penzoil, as little as an ounce of water in the lower unit can spell doom for bearings and gears. The solution is as simple as the sea is salt. Regularly crack the bottom drain screw and determine whether oil or water issues forth. Also look for wads of mono filament fish line has wrapped around the prop shaft, where left in place it will worm its way right through the propeller shaft seal.
Overheating is one of the major causes of premature death for marine engines. To prevent such a demise pay attention to engine temperature. Consider rotating the fuel gauge to its needle point straight up when registering normal engine temperature. Then if the temp begins to rise you'll see it immediately. Naturally you'll also regularly inspect cooling system hoses for age or damage.
An out of tune engine spills un-burned gasoline or diesel fuel down the sides of the cylinder walls. Raw fuel washes away oil. Metal on metal causes extreme engine wear. Symptoms of an out of tune engine include rough running, lethargic performance, and sometimes, exhaust smoke. With gas engines the fix is often as straightforward as replacing spark plugs and wires and cleaning the flame arrestor. On a diesel one or more of the injectors may require rebuilding.
© Copyright 2007 by Tim Banse