The price of failing to keep a maintenance vigil may be as low as the cost of a broken alternator belt or as high as the loss of an entire vessel. In my experience as a boat yard manager I have come to believe that the expenditure of time, effort and expense, or some combination of the three, will enhance the safety and reliability of your vessel.
As the old axiom goes, you can spend a little now or a lot later. Many maintenance tasks, in their preventive form, are substantially less costly than those that reach the failure stage. The difficulty lies in knowing just what to maintain and when. Fortunately, as time has progressed the quality and quantity of literature produced by marine engine and equipment manufacturers has improved. Much of the information detailed in the following paragraphs can be found in your owner’s and maintenance manuals, as well as at manufacturer’s Web sites.
Fresh fluids
Nearly all inboard marine engines share a degree of commonality; they require certain fluids such as crankcase oil, coolant, and gear or transmission oil. Additionally, the tender’s outboard requires lower unit oil and, if it’s a four-stroke, it needs crankcase oil as well.
A common mistake made in this realm is the use of the wrong type, or weight, of crankcase oil. Diesel engines require their own special mix of additives to deal with increased soot and acidity. All diesels call for oil bearing the “C” prefixes, such as 15W-40 CC, CD, CE and so on. The C denotes compression ignition (some texts say the C indicates “commercial”), as opposed to spark ignition, which is what gasoline engines use, indicated by an “S” and again, some say this denotes “service” rather than spark. The second letters, C, D and E in this example, indicate the additive package. The higher into the alphabet this second letter reaches, the more recent, sophisticated and, hence, desirable the additives. Regardless of what you may have heard, all diesels must use C-prefix oil and most gasoline engines specify the S prefix. Using C-prefix oil in a gasoline engine is usually not harmful, however, using S oil in a diesel often is harmful and, thus, strictly prohibited. The required weight, whether single or multi (30 vs. 15W-40, for instance), depends on manufacturer and climate. Check your owner’s manual for this information.
Oil change intervals vary from manufacturer to manufacturer, however, the generally accepted rule is to carry out a filter and oil change every 100 to 150 hours. If you run your engine under light loads for much of the time (which is often the case for generators and propulsion engines that are used for battery charging), then this interval should be decreased to 50 to 75 hours. Idling engines tend to run comparatively cold, which makes for poor combustion characteristics. This leads to oil that quickly becomes laden with particulate matter, soot and moisture, which ultimately leads to the formation of acids. Acidic oil is harmful to and will often pit or etch the polished, internally lubricated components within your engine, such as camshaft lobes, crankshaft journals, lifters, etc. Prior to extended storage or seasonal lay up, the engine oil should always be replaced. Leaving old, sooty, acidic oil in an engine will only serve to shorten its life. Be certain to circulate the new oil through the engine for at least 10 minutes of running time before putting the engine away for extended storage. This will ensure that all the internal parts have been flushed and coated with a layer of new, clean oil.
Coolant, or anti-freeze, is probably the most often neglected of engine fluids. This is unfortunate because it has a great deal of influence on the overall health of your engine. Coolant does wear out, and you don’t have to wait for it to look like coffee to replace it. In fact, it should look clean when it is replaced. If this is the case, then you can rest assured that you haven’t waited too long. Most engine manufacturers specify renewal intervals based on engine hours or the passage of time. My recommendation is for replacement every two years or 500 hours of operating time, whichever comes first.
Just as with oil, there are specific requirements for coolant, depending on the type of engine in which it is used, and this is particularly so for diesels. Check the owner’s manual for your engine. Some diesels, particularly those with “wet” cylinder liners (the outside of the liner makes direct contact with the coolant, as opposed to parent bore and dry liner engines), are susceptible to cylinder liner excitation, which leads to a process known as cavitation erosion. This occurs because of the high compression and frequency at which diesels operate. Vapor bubbles are repeatedly created and imploded within the coolant against the cylinder wall. Each time an implosion occurs, with a force that may exceed 15,000 psi, a few metal molecules are worn away. Eventually, enough metal may be removed to cause cylinder wall damage and a subsequent catastrophic engine failure.
To prevent cavitation erosion, as well as ordinary rust and corrosion, use only the coolant specified by your engine’s manufacturer. Also, some engine manufacturers may call for the periodic inclusion of an additive to further inhibit the cavitation erosion process.
A common mistake often committed by the do-it-yourself mechanic involves the use of ordinary tap water for the coolant mix. Many municipal water supplies and wells are high in mineral content. These minerals, once in the cooling system, often settle out in low spots within the cooling jacket, exhaust manifolds and heat exchanger, creating local hot spots and impeding water flow. A fraction of an inch of mineral scale may possess the insulating properties of several inches of solid iron. Localized over-heating is a particularly insidious problem in that your engine’s coolant temperature gauge will typically not register the problem. Overall, the engine and its coolant are not overheating; however, certain areas within the cooling system may actually be running well above their designed temperature range. Additionally, the presence of minerals may actually accelerate corrosion for certain metal components. Use only distilled (not spring) water in a 50/50 mix with the proper coolant and anti-cavitation additive. Never use 100 percent undiluted coolant unless it is specifically formulated for full-strength use.
While the use of the correct crankcase oil is critical, it’s not the only component that requires liquid lubrication; the transmission, or reverse gear, calls for its own special kind of oil. Depending on the manufacturer, model and vintage, this may be anything from 30-weight crankcase oil to automatic transmission fluid to 90-weight gear lube. It is vitally important that the correct fluid be used. If you fail to observe these specifications, severe damage and wear may result to the bearings, clutches and gears within the transmission, eventually leading to its seizure. Some gears call for non-detergent oils. While available, these are not usually found on the shelves of your local auto parts store or marine chandlery; they sometimes require a special order. If you intend to carry out reverse gear service, plan ahead by having the correct fluid on hand. Whether this fluid requires a special order or not, it’s a good idea to keep it, as well as crankcase oil and coolant, onboard for topping up.
Unlike the crankcase, transmission fluid is not exposed to combustion byproducts such as soot, sulfur and fuel. However, it does wear out, suffering from viscosity breakdown, and metal and moisture contamination. Service and replacement intervals are usually indicated within the engine or gear service manual. If this information is unavailable (or even if it is), my recommendation is to replace it annually, regardless of the hours that have been accumulated. This may be considered by some to be overkill, however, transmission repair and/or replacement is always expensive, and there are times when you need a reliable drive train, particularly in times of crisis (clawing off a lee shore or in grounding/falling tide scenarios). Replacing the quart or two of fluid and filter, if equipped, is comparatively inexpensive insurance against failure.
Carefully check the fluid that’s been drained. If it smells burnt, the transmission cooler may not be operating properly, the fluid may be well past its replacement interval or some adjustment may be in order. Does the shaft turn slowly while the transmission is in neutral? If so, it’s in need of some adjustment, service or outright repair. Fully 1/3 of the transmissions that come to my boat yard are improperly adjusted in that the shift cable prevents the transmission’s shift lever from fully engaging or disengaging the gear. The shift lever located on the transmission should move fully into its detent in each gear position: forward, neutral and reverse. If it does not, it will accelerate wear and create excess heat within the transmission.
If the fluid looks milky or like a strawberry milkshake, seawater or coolant may be mixing with the transmission fluid because of a faulty cooler assembly. If the oil looks sparkly or like metal flake paint, a bearing or gear may be failing, depositing metal filings into the lubricant. Any of these anomalies call for closer inspection and perhaps the services of a skilled marine transmission shop.
Finally, follow the directions for your particular gear to determine the proper fluid level. Some gears call for the fluid to be checked with the fluid warm but engine off, while others call for the engine running at operating temperature and idling in gear.
Outboards have some special requirements. Most call for a proprietary high viscosity lubricant, sometimes synthetic, which provides the requisite lubrication for the hard life many outboard gears lead. Because of the expense involved in repair or replacement of these complex pieces of equipment, outboard lube oil must be checked and replaced with near religious regularity (at least annually).
When draining outboard gear lube, do so into a clean container so that it may be inspected for the two main signs of trouble, water and metal filings. If the engine hasn’t been used in some time, water may run out freely before the oil begins to drain or, if used recently, it may be emulsified with the oil, looking something like mayonnaise. Metal filings or chunks are signs of trouble within and are usually obvious thanks to the magnetic drain plug fit to most units.
Follow your outboard owner’s manual for filling directions, and use only the manufacturer specified oil. Small lube oil pumps are available at most chandlers, making filling relatively easy. Remember, in order to prevent air locks, most outboards are filled from the bottom up.
Belts and sheaves
Engine belts and sheaves require regular inspection, service and periodic replacement. The primary enemies of the traditional V-style engine belts are misalignment and incorrect tension. Both of these problems are usually evidenced by belt dust being deposited on the front of the engine or within the engine compartment. Don’t ignore this signal. Misaligned belts wear very rapidly and nearly always lead to premature failure.
Carefully inspect all engine belts, ensuring that all sheaves that share a single belt are parallel and utilize the same cross section width. The belt must fit all of these sheaves identically. A belt that properly fits its sheave will not bottom out in the V groove, nor will it stand proud of the sheave by more than 1/16 of an inch. Ideally, the belt walls should ride in the middle of the sheave groove. This is usually easy to confirm by inspecting the area where the paint has worn off of the sheave groove.
Under- or over-tensioned belts will both lead to shortened belt and equipment life. Under tensioning, the most commonly experienced problem will cause belts to slip. This will lead to overheating of both the belt and the sheave, which often drives an alternator or pump. These devices will then be damaged in turn by excessive heat, particularly alternators. Purple or bluish sheaves are evidence of this type of slippage and overheating. (An alternator sheave that’s been severely overheated may cause demagnetization, which will prevent it from producing charge current.) Slipping belts often produce copious amounts of belt dust. This belt detritus is so fine that it is often mistaken for oil as it’s deposited around the front of the engine or on the alternator. In addition to making the engine room dirtier, belt dust easily becomes airborne and is subsequently sucked into the alternator where it deposits itself on the windings and other components. Here it acts as an insulator, leading to alternator overheating and failure. Finally, this dust is also sucked into the engine’s air intake, where it either clogs the air filter, if equipped, or deposits itself on valves, pistons and rings. You shouldn’t need any more reasons than those detailed above to avoid slipping belts.
Highly polished sheave grooves and belt bearing surfaces, a condition known as “glazing,” are evidence of slippage as well. Proper belt tension is sometimes difficult for the novice to determine, however, there is a method the uninitiated can use to get this right. Depending on the type of belt, roughly 4 pounds of pressure should deflect the belt by 1/64 of an inch for every inch between sheave centers. For example, if the distance between sheaves was 12 inches, the deflection would be roughly 3/16 of an inch. (If you can still find one, Gates, a major belt manufacturer, offers a simple belt tension-testing tool.) A less scientific approach to belt tension calls for tightening the belt just enough so that it does not slip, and no more. Accessories that utilize large diameter sheaves, like many raw water pumps, tend to require less tension than highly loaded, smaller sheaved devices, such as alternators. The watch phrase here is regular inspection – check your belts regularly for signs of slippage. Unfortunately, other than belt tension itself, there are no early warning signs for over-tensioning. Correct alignment and tension, along with a proper match between belt and sheave, makes for long-lasting belts.
If you are fortunate enough to have an engine that is equipped with one of the more modern serpentine or Micro-V belts, then these problems are all but eliminated in that many of these utilize an automatic tensioning device. Your primary responsibility is to ensure that the automatic tensioner is operating properly (it should be free to move, placing constant tension on the belt and parallel with the belt and other sheaves. When tensioners fail, they usually do so by falling out of parallel) and that the belt is replaced once it’s passed its service life. Any signs of cracking in the rubber or visible belt filaments, usually white, thread-like strands, are an indication that the belt is ready for replacement. All belts, whether V or serpentine, should be replaced every three years or at the first signs of wear.
As great as these low maintenance, long-life serpentine belts are, they have one drawback – releasing the tension will require some unusual, if not special, tools. My advice is to carry out a belt replacement evolution just for practice, at least once, while you have ample time and are dockside. Don’t wait to carry out this service for the first time under extreme circumstances.
If your engine is equipped with a timing belt, as so many new diesel engines are, then it, too, requires periodic inspection and replacement. Guidelines vary, but a rule of thumb calls for semi-annual inspection (it’s often under a plastic cowling) and replacement ever 1,000 hours or five years, which ever comes first. If this belt should fail, it may cause considerable damage to the pistons and valves, so though the replacement interval is lengthy, it must not be ignored.
