Many outboards and most inboard/outboards come equipped with power trim which raises or lowers the drive unit. In this case the term “trim” refers to the running position of the engine drive unit. Although most people know that the trimming movement raises and lowers the bow, many are unaware that it also can effect steering and performance. When you trim your drive unit either “in” or “out” you may feel a pull on the steering wheel either to the right or left.
If the steering pull grows beyond a slight pull, an inadvertent release of the wheel can cause the boat to go into a sharp turn and passengers could be thrown around, or even out of, the boat. Be sure to keep a firm grip on the steering wheel. The three positions of trim and results are as follows:
Believe it or not, most people do not completely understand the full role of how the steering wheel (its diameter and placement) plays into how the steering system works. Usually “aesthetics” is the basis to decide what type of steering wheel one chooses. Yes, that is important, BUT, the diameter of your steering wheel or the actual radius at which you are turning it becomes a major part of the equation if you go with passive steering. Bigger diameter wheels equals less RIM FORCE in order to turn. Think of it like a longer wrench when trying to get a bolt tight, or loose. Call it “LEVERAGE”. If you only have room for a small diameter steering wheel, then in most cases, you will need more turns lock-to-lock to compensate for the decreased leverage you have turning the wheel. Large diameter steering wheels give the operator more leverage to overcome higher pressures within the system and usually require less turns lock-to-lock overall…
STEERING LINES & FITTINGS
Here is where you will see major differences in what is used or can be used in hydraulic steering installations. Most smaller “production boats ( from 18 ft. outboard powered boats to 40 ft. lower cost diesel powered boats) usually employ common type brass pipe and tubing compression type tubing fittings and un- reinforced thermoplastic hose. Most get by with this type of lower cost equipment, but realize that you get what you pay for. Most of these systems are “barely adequate” as to performance and overall system longevity and we consider the use of un-reinforced thermoplastic tubing (typically nylon) to be applicable only to “lake boats” and outboard engines at best. IMO, using SAE or JIC flare fittings with copper or metallic tubing or pipe or in combo with reinforced non-metallic hose is the right solution for all marine applications. You must also be careful about using any type of brass fittings that are not rated for working pressures of at least 1000 PSI, and are robust in wall thickness especially with internal threads.
Assembly should be done using high quality pipe dopes, anaerobic sealants, & sometimes even epoxy compounds specifically made to withstand petroleum based liquids and are designed for pressures of more than 2000 PSI. Avoid Teflon tapes entirely as you do not want any shredded pieces getting inside the system Passive steering system pressures should be designed so that 90% of the time, line pressures fall under 500 PSI. This is determined by RAM SELECTION or size. Larger displacement rams make for more turns but also keep pressures low. Steering wheel or RIM force becomes uncomfortable much above 5-8 lbs., so sizing the ram to keep pressures low means less rim force or effort to turn the steering wheel…
With power steering, pressures are usually higher and can play havoc with a ram if undersized. The operator, typically, never knows the difference until something back by the rudder breaks. Sized right though, power assisted steering is sometimes the only practical choice when the operator wants 2-4 turns lock-to-lock and needs a small diameter steering wheel.
The term “running gear” refers to a boat’s propeller(s), shaft(s), strut(s), trim tabs, intakes (through-hulls), intake covers, transducer(s), knotmeter, keel cooler(s)
(when applicable), grounding plate(s), and line cutter(s). With just a few barnacles on your boat’s running gear you might experience
- vibration when the boat is in gear
- black smoke coming from your exhaust
- increased fuel consumption
- “prop walk” or an inability to control the direction of your boats movement
- lack of ability to draw water through your intakes
If these symptoms are ignored, or if a boats is run with heavy barnacle growth on the running gear it could result in much more serious problems such as: At Siebert Yacht Management we don’t just scrape propellers; we clean your boat’s running gear in an effort to restore your boat to its peak
Tips on adjusting the engine, bearings, and shaft for maximum efficiency. Many consider running-gear alignment to be a black art. At a yard I once managed, I clearly recall watching a contractor, who specialized in this work, take a decidedly seat-of-the-pants approach to “calculating” shaft weight and the associated sag or droop.
When it comes to ensuring that an inboard propeller shaft and its supporting bearings are properly installed and aligned, there might be some art, but there’s no magic. The practices and procedures are straightforward, and if you take care to ensure accuracy and precision, the results should be predictable. There are essentially two types of alignment. The first is positioning the engine relative to the shaft. The second is more difficult: adjusting the shaft bearings and/or their supports.
Engines and motor mounts are designed to accommodate some adjustment. Most mounts employ jacking screws that allow for a narrow-range change of elevation. Side-to-side adjustment is often facilitated by the mount’s elliptical-base fastener holes—again, with a limited range. In this type of adjustment the engine is moved relative to the position of the shaft, because the shaft’s position is assumed to be nonadjustable. Unless the installation includes a thrust bearing of some sort, all the thrust created by the propeller is transmitted to the vessel’s hull via the motor mounts. The boat is pushed through the water by virtue of the mounts and their associated hardware. Keep this in mind as you select and install components.
Because you should tighten all fasteners with a torque wrench, avoid thin fender washers that are easily distorted when you install mounts. Likewise, through-bolts, locking nuts, and machine screws should be favored in place of self-tapping lag screws. Because of the pressure and leverage imparted on motor mounts, installers and those performing adjustments should avoid maximum extension of the mount’s adjustment screw thread, which could cause cyclical loading-induced failure. If more of the mount’s adjustment screw threads are visible under the engine support bracket than on top of it, a shim should be installed beneath the mount’s foot plate to close the gap.
Ideally, when adjustments are complete, the engine bracket should rest somewhere in the middle of the adjustment stud. Shim material should be rugged, incompressible, and resistant to splitting or fracturing. Steel or aluminum plate works well; prefab FRP such as GPO or G10 is also suitable. Avoid high-density polyethylene, including King Starboard and other non-reinforced plastics.
The face of the transmission output coupling and the face of the propeller shaft coupling must be parallel, or made parallel, to within no more than 0.004″, or 0.1mm (rules of thumb for this calculation vary; the stated figure is from a shaft manufacturer). Inspect the faces for damage, scoring, corrosion, dents, and distortion of any sort. Any irregularities will make it difficult, if not impossible, to measure for alignment analysis.
What’s often not well understood about alignment is the requirement that the theoretical centerline of the shaft to be centered on the transmission output coupling.
Yard personnel often ask, “How difficult should it be turn a shaft and prop when the vessel is blocked?” I know a shaft that’s too tight when I encounter one, but that’s not a helpful answer to others making a determination whose results could lead to costly repairs. Here’s a rough rule of thumb that I go by: provided the vessel is properly supported, and the bearings are lubricated with diluted dishwashing detergent, even large shafts—say 2.5″ (63.5mm) in diameter, 18′ (5.5m) long, and supported by three bearings—should move with no more effort than an adult can impart with one hand.
That’s subjective to be sure. Recently, I was able to lift my entire body weight off the ground in an attempt to turn a 3″-diameter (76mm) by 18′-long two-bearing shaft installation. Clearly it was too tight, and the bearings and shaft likely needed realignment.
Shaft alignment is typically thought of as nonadjustable. As mentioned earlier, that’s not strictly true. When the shaft supports, strut, or keel/shaft log-mounted cutlass bearings are installed, their position should be carefully chosen to ensure that they are parallel and share the same theoretical shaft centerline. If the bearings are not aligned with each other, if they are not parallel, or if they deviate from the shaft centerline, the shaft and/or bearings will be distorted during installation. The classic pinched bearing is an indication of that, as is the shaft that’s exceptionally difficult to turn from the propeller end. The distortion induces a range of maladies, including excessive bearing and shaft wear, vibration, increased drag, and diminished fuel efficiency and performance.
If the bearings are not properly aligned with the shaft at the time of initial construction or installation, then they or their supports, the struts, shaft log- or keel- mounted bearing(s), must be repositioned. While this wouldn’t strictly fall under the definition of “adjustable,” modifying the position of these bearings becomes the only means of resolving the misalignment. So, shaft alignment is adjustable, but not easily. I’ve supervised many shaft and support realignments. While there are several methods, my preference is to begin by assessing the misalignment with a laser alignment tool. The full procedure is beyond the scope of this article, but in short: by placing a laser in the aftmost cutlass bearing, with the shaft out and pointing it toward the engine, you can determine, with purpose-made targets, if the aftmost bearing and any intermediate bearings are properly aligned. The laser pinpoint should land in the middle of the transmission output coupling as well as the targets placed in any intermediate bearings, confirming that the theoretical shaft centerline is aligned with the output coupling centerline.
Engine alignment also can be confirmed by installing the laser in the coupling shaft bore and shining it aft to targets placed in the bearings. A final engine alignment must still be confirmed by coupling clearance measurement after the vessel has been launched and running gear components have settled. Yards that routinely confirm or adjust shaft alignment typically make or have made a series of targets and jigs to support and aim lasers through and onto a variety of bearing and coupling sizes and types.
If a bearing is out of alignment, from either a centerline or parallel point of view, it must be adjusted. If the bearing is strut-mounted, the strut must be removed and a base wedge of cast epoxy or fabricated FRP installed to relocate the bearing. Again, repositioning is confirmed with a laser and target. The strut must be held firmly in place, with the laser on target, until the epoxy cures. Afterward, the waxed strut is removed, cleaned, and bedded and fastened in place. If the bearing is mounted in a keel or shaftlog, the process can be more challenging; however, casting in the realigned position remains the order of the day. In some cases, a section of shaft can be used to align both ends of a keel- or shaftlog-mounted bearing during the casting process.
A final variable to consider is shaft sag. The shaft section that lies between the forward most bearing (in a multiple-bearing installation) and the coupling will droop or sag under its own weight and the weight of the coupling. If the droop is not corrected before the shaft and transmission couplings are aligned, then a bow, or curve, will be built into the finished assembly. If you’re skeptical of just how much a shaft can droop, allow the length of shaft from the bearing to the transmission, with the coupling installed, to hang off a sturdy workbench or table. Then measure the difference between the distance from the floor to the shaft at the table and the floor to the shaft as it enters the coupling. The result is the droop.
Sag can be factored out by aligning the centerline of the transmission output coupling with a laser shot from the cutlass bearing. If a laser shaft alignment has not been carried out, and if the shaft has not been removed, the droop can be negated by calculating the weight of the unsupported shaft, dividing that by 2 (because one end of the shaft is supported), adding the weight of the coupling, and then lifting, or “neutralizing,” the weight using an industrial hanging scale or compression scale under the shaft.
For example, 4′ (1.2m) of 2″ (51mm) shaft weighs 42 lbs. (19 kg), divided by 2 is 21 lbs. (9.5 kg), plus the weight of the coupling—which we’ll say is 22 lbs. (10 kg)—equals 43 lbs. (19.5 kg). Lifting 43 lbs. at the coupling end of the shaft will negate the effect of the droop. In practice, the droop is negligible for small-diameter shafts and for shafts whose unsupported overhang is comparatively short, making the above procedures unnecessary. For long spans and heavy shafts/couplings, those steps are worth the effort.
Roughly one-third of the new vessels I encounter suffer from some form of shaft misalignment—either misaligned bearings or shaft droop. The next time someone mentions checking alignment, take a moment to discuss exactly what’s meant and what’s involved in ensuring alignment is right in every respect.
With high fuel prices, now is a good time to fit the best propeller. The first step in assessing whether an installed propeller is suited to the vessel and engine is observation. Does the vessel perform as well as others of similar power and design? If the answer is no, it is important not to jump to the conclusion that the propeller is incorrectly specified.
Other factors must also be considered, such as the condition of the underwater surfaces of the hull. When the vessel was last cleaned and painted? What is the condition of the propeller – is it clean, undamaged and smooth? What is the power of the engine and what condition is it in –
should it deliver the same amount of power?
The propeller may be incorrectly specified if:
- The engine fails to achieve designed RPM and is overloaded;
- The engine passes designed RPM at full throttle, over-revs and is under loaded;
- The propeller is overloaded and shows signs of cavitation’s and surface erosion.
Therefore, a preliminary check is advisable before consulting a propeller company or naval architect for further assistance. A simple method for making a first estimate of what the basic parameters of selection of a propeller for their good operation is described next. Engine overloading wastes fuel. Overloading of the engine through the installation of a propeller with too much pitch is the most common source of fuel inefficiency. Overloading can also result from the use of a propeller with too large a diameter, but this is less common. With inboard diesel engines, a sure sign of an overloaded engine is a lot of black smoke in the exhaust before reaching the designed RPM. Overloading can result in burnt valves, a cracked cylinder head, broken piston rings and a short engine life. It is important to remember that, with a diesel engine, it is the load and not the revs that determine fuel consumption. Therefore, continuous overloaded operation results in unnecessarily high fuel consumption and increased maintenance costs.
Engine under loading reduces performance. Engine under loading from the installation of a propeller with too small a diameter or of insufficient pitch affects vessel performance. It can also result in engine damage if it is allowed to rev above its specified maximum RPM. Engine under loading is likely to be accompanied by low fuel consumption and, often, propeller cavitation. If the preliminary check indicates that a change should be made to the propeller, it is worth remembering that some small changes to the pitch can be made without the expense of buying a new propeller. The re-pitching of a propeller is a specialized task, however, and the propeller will need to be sent to a manufacturer for reshaping.
Trawlers need special consideration. The design of trawler propellers requires special attention, as the propeller has to perform under two completely different operating conditions – towing and “free running”. With a fixed-pitch propeller it is impossible for the propeller to be operating at optimum design conditions while both free running and towing. The propeller designer must strike a compromise based on the time the vessel spends operating in the two situations. For vessels working a great distance from their home port, the benefits to be gained from designing a propeller with increased towing power (and therefore catching capacity in the case of a trawler) may well be outweighed by the increased cost of fuel for the transit journey, and the design will err towards a higher-pitched propeller. A day boat operating relatively close to its homeport would inevitably have a propeller optimized for towing.
THE MINIMUM INFORMATION REQUIRED FOR SIZING PROPELLERS
1. VESSEL LENGTH (also water line length, beam, draft – if known)
2. VESSEL OPERATING WEIGHT (very important)
3. VESSEL STYLE & USAGE (hull design and duty)
4. NUMBER OF ENGINES
5. MAX. BRAKE H.P. AND R.P.M.
6. GEAR REDUCTION RATIO _____: 1
7. PROPELLER ROTATION – L/H or R/H
8. EXPECTED VESSEL SPEED
9. MAXIMUM DIAMETER PROPELLER POSSIBLE TO FIT (MEASURE DIA OF OLD PROP THEN THE
10. TAPER BORE DIMENSIONS AND SHAFT SIZE (USUALLY CAN BE MEASURED FROM THE OLD PROP)
Getting as much information including any other known data e.g. the present propeller, (diameter, pitch, style, number of blades) your vessel’s present performance – best speed at wide open throttle and maximum engine R.P.M. achieved are all helpful in getting the right propeller for your boat. Photos, G.A. drawings and aft end section lines assist in achieving a more informed optimum sizing suggestion. Accurate information is essential. Guessed data and estimations will most likely lead to an unsatisfactory outcome wasting fuel and compromising performance.
Propellers are available in Manganese Bronze, Nickel Bronze Aluminum and extra strong Aqualloy. These metals are well known for their strength, durability and repairability. Other alloys are available for special applications.
Whenever different metals are placed in a conductive liquid, such as salt water, you create a battery. If you connect these pieces of metal together, current will flow. This current, trying to equalize the conductivity of the metals, will be removing metal from one of the metal pieces. This removal is called “electrolysis”. If the piece being removed is the zinc in your flashlight battery that is good, but if one of the pieces is your propeller it is bad.
When you pull your boat to do the bottom you may wonder what those pitted, ashen-white pieces of metal are on your shaft, rudder or possibly on the transom. These are called zincs and, as luck would have it, are made of zinc. The zincs you use on a boat are called “Sacrificial Anodes.” Zinc is used because it has a higher voltage in the water so the current will be more inclined to flow from it than from your propeller.
To complete the electrical circuit, the zincs must be connected to the items they are intended to protect. Usually this is no problem because the zinc is bolted right to the shaft or underwater housing. Non-metal boats will usually have a copper bonding wire inside that connects all the underwater metal items together so they all share the protection from zinc anodes. Since engines use the metal frame as the negative battery connection and the engine is connected to the prop shaft, the engine and the negative side of your 12 volt system are also part of this bonding connection. This bonding wire may also be connected somewhere to the rigging. This is not for electrolysis protection but for some protection from lightning strikes to conduct it into the water through the items connected together.
If other currents are allowed to get into this bonding circuit they can easily overpower the small voltage available from your zincs and defeat the protection you need. This is usually the most destructive form of electrolysis and you notice it because your zincs get eaten up very quickly trying to keep up. Under normal circumstances, zincs should last at least a year if they are working normally and much longer if you don’t have any problems. If they are being “sacrificed” in a shorter period you need to find where the external current is getting in.
The most common source of this external current is the shore power connection, sometimes referred to as stray current. Docks are notorious for bad wiring and often the ground lead is not connected to ground, but is connected to the neutral and is being used for carrying current to a poorly wired boat. The purpose of the shore power ground lead is to provide a return path for current if there is a short circuit or power leakage from an appliance or the wiring on the boat.
There are other sources of electrolysis that you can’t correct. The boats on each side of you in the marina may be connected together through the dock ground lead and one may be eating up the zincs rapidly on the other. If you sit between them, this current may take a short cut by going in an item near one boat and exiting via your zinc near the other. This will eat up your zinc too, even though you are not connected to the other boats. The best solution here is to use zinc fish while you are at the dock. They are large lumps of zinc, often cast in the shape of a fish, that are cheaper and easier to replace than the zincs on your shaft.
The “fish” come with a copper wire already attached which is also used to hang them in the water. They have an alligator clip on the end of the wire and this should be connected to the negative bonding circuit on your boat. If it is not conveniently available in the cockpit in the vicinity of the prop, you might consider installing a stainless bolt for clipping it to, with the head of the bolt inside the deck connected to the negative bonding system. Clipping it to the shrouds or railing will only work if somewhere on the boat the shrouds are connected to this boat negative bonding system.
Making sure that your boat is regularly maintained not only keeps it looking clean and great, but it can also increase your boat’s life. Consistent boat detailing also makes it much less complicated to maintain the boat’s cleanliness and reduces the cost of boat maintenance. Boat detailing is essential because hulls usually develop oxidization stains when left unattended for a long time. You can definitely avoid this as well as other types of damages to your boat by hiring boat detailing professionals on a regular basis to keep your boat always looking as if it is brand new.
It does not matter whether you use your boat frequently or you have kept it stored for quite some time, it can absolutely benefit from a professional boat detailing. Consistent care and appropriate detailing are important steps in the proper maintenance of your boat, whether you use it to fish or other recreational functions. Professional Boat Detailing experts have the necessary experience and tools handle all your boat cleaning requirements. From basic yacht maintenance to commercial boat detailing, you can always rely on boat cleaning professionals for the best cleaning results. They can get rid of all types of dirt and grime that have accumulated on the boat’s exterior, making sure that the boat looks its best.
Whether it is the boating season or not, it is best to keep your boat in tiptop condition. Schedule your boat for complete detailing. The boat will look definitely better after you clean every nook and cranny of especially everything underneath the rub rail. Having a boat detailed will help re-commission the boats before the boating season. A boat owner will always put top quality services at the top of his boat care requirements list. As a boat owner, you will definitely require the assistance of expert boat detailing specialists every now and then.
Nevertheless, one has to be ready to do a few small and uncomplicated tasks in between detailing schedules to maintain the boat and keep it looking good for a long time. Have a Regular Boat Detailing Schedule Your boat is regularly left bare to the elements such as sun, wind, water. Exposed to these, the boat’s body will show signs of wearing in no time, even when it is dry-docked for so many months. Making sure that you have a regular boat detailing schedule will help in preserving the good looks, functionality, and worth of your boat, and this is great especially when you reach the point that you want to resell it. A professional boat detailing expert will be able to immediately see potential issues which require instant action, and this will save you from having to spend lots of money for repair or replacement in case the problem progresses. You do not want your boat failing you during an important business meeting or family event.
Thеrе аrе sеvеrаl rеаllу іmроrtаnt points tо bе mаdе аbоut thе engine maintenance. Regular oil changes, proper fuel filtering, аnd thе lіkе notwithstanding, thе mоst effective wау tо derive maximum longevity frоm уоur boat’s engine іs tо operate іt wіthіn іts sресіfіеd horsepower range. Contrary tо common belief, thіs саnnоt bе guaranteed bу simply bу operating thе engine bеlоw іts maximum rated rpm, fоr example, bу running аn engine wіth а maximum rated 2300 rpm аt 1800 rpm. Тhе fact іs уоu саn overload аn engine, аnd consequently increase іts rate оf wear, аt јust аbоut аnу rpm. Here’s why.
POWER ІΝ RESPONSE ТО ENGINE LOAD
An engine develops power іn response tо load. Аt аnу time, уоur engine mау bе producing mоrе оr lеss horsepower thаn іts rating specifies. Тhе mоrе horsepower thе engine produces, thе mоrе internal heat аnd stress іt produces. Ѕіnсе thеsе factors contribute tо wear, increased horsepower (оr, mоrе accurately fоr оur purposes, increased torque) mеаns shorter engine life. Тhеrеfоrе, thе key tо maximizing engine life іs tо kеер torque аnd horsepower production аt оr bеlоw thе maximum levels sресіfіеd оn уоur engine’s rating curve. Ноw dо уоu dо thаt, уоu аsk, sіnсе уоu саn’t measure horsepower wіthоut а dynamometer (а bench- оr floor-mounted resistance brake)? Оr саn you?
Horsepower іs а measure оf work accomplished, аnd іs thе product оf torque аnd engine rpm. Оthеr factors held constant, torque іs produced bу combustive force іn аn engine’s cylinders acting thrоugh іts pistons, connecting rods аnd attached crankshaft. Combustive force іs determined bу thе quantity оf fuel burned, whісh іn tum depends оn thе throttle setting. Fоr instance, іf уоu nееd full throttle tо reach 1800 rpm оn аn engine wіth а rated maximum rpm оf 2100, thаt engine іs lіkеlу developing mоrе horsepower thаn іt іs rated tо produce аt thаt point оn іts rpm curve. Ѕо, thаt engine іs lіkеlу wearing оut аs а faster rate thаn thе engine manufacturer anticipates оr judges acceptable. Yоu саn draw thе sаmе conclusion іf уоur engine fails іn operation tо bе аblе tо achieve іts maximum rated rpm оr takes аn excessively long time tо dо so.
A good wау tо kеер tabs оn torque аnd horsepower production іs tо monitor fuel consumption. Ву comparing actual fuel burn wіth thаt charted оn аn engine’s rating curve, уоu саn judge whеthеr thе engine іs bеіng overloaded оr nоt. Іf уоur engines аrе expensive units, thіs mау bе а good reason tо install fuel flow metering, іf уоu dоn’t аlrеаdу hаvе electronic monitoring thаt рrоvіdеs thе needed іnfоrmаtіоn. Моrеоvеr, understanding whаt percentage оf уоur engines capacity fоr power production уоu аrе асtuаllу usіng gіvеs уоu а good indication оf а number оf оthеr key items, fоr example, hоw well уоur reduction gears аnd props match thе engine’s rated power curve аnd, thеrеfоrе, whеthеr уоu саn expect аnу improvement wіth adjustment tо suсh factors.
Perhaps еvеn mоrе importantly, sіnсе fuel bum varies wіth load, total fuel consumption іs а better indicator оf accumulated engine wear thаn engine hours. Аs а senior applications engineer аt Caterpillar оnсе told mе, “Іf уоu run а 10,000-hour engine оnlу undеr light loads, independent оf rpm, іt will lаst а heck оf а lot longer thаn 10,000 hours bеfоrе needing аn overhaul.” Gіvеn thаt fuel burn іs closely linked tо torque аnd horsepower production, аnd thеrеfоrе heat аnd stress, hе pointed оut furthеr thаt, “Тhе mоst practical field indicator fоr determining accumulated engine wear іs thе total, accumulated amount оf fuel burned.”
Indeed, today, mоst major marine engine manufacturers including Caterpillar, hаvе programs fоr scheduled maintenance thаt аrе based оn accumulated fuel consumption, аs thе preferred alternative tо engine hours. Тhе principle іs straightforward. Тhе higher thе engine loading, thе mоrе fuel уоu рut thrоugh уоur engine іn а gіvеn period оf running time (engine hours), аnd thеrеfоrе thе mоrе rapidly thе engine will wear. Тhе converse іs thаt а generally lightly loaded engine will wear lеss durіng thе sаmе period оf running time. Аll оf whісh іs а vеrу strong argument fоr basing maintenance intervals оn accumulated fuel burn, rаthеr thаn engine hours.
HOURS ОF HORSEPOWER
An engine’s fuel curve depends оn іts rating, whісh relates tо specific load аnd duty conditions. Тhе precise nomenclature chosen varies sоmеwhаt frоm manufacturer tо manufacturer, but sоmе common rating designations аrе: 1) continuous, 2) intermittent, аnd 3) maximum intermittent duty. Аn engine rated fоr continuous duty саn bе operated аt іts maximum rating fоr іts entire designed life, і.е., TBO оr time bеtwееn major overhauls. Continuous duty horsepower ratings аrе generally applied tо commercial applications аnd аrе typically lower thаn оthеr ratings. А rating fоr intermittent duty allows fоr mоrе horsepower tо bе drawn оut оf а gіvеn engine, but nоt оn а continuous basis. Engines rated fоr maximum intermittent duty typically offer thе highest horsepower fоr а gіvеn engine, but dо sо оnlу fоr vеrу brіеf intervals, іn bеtwееn whісh thеу must bе operated аt intermittent оr continuous duty levels іn order tо achieve thеіr rated TBO.
Maximum intermittent duty rated diesel engines оftеn hаvе thе shortest projected TBO, fоllоwеd bу intermittent duty rated engines, аnd thеn continuous duty rated engines, fоr whісh will bе projected thе highest TBOs. Whеn sоmе manufacturers rate fоr intermittent оr maximum duty, thеу limit engine hours аt higher load levels tо ensure thеіr engines lаst thе projected TBO. Оthеrs, hоwеvеr, sау thаt thеіr intermittent оr maximum duty engines will lаst fоr thе sаmе number оf hours аs оnе rated fоr continuous duty, provided thе engine’s load history conforms tо thе specifications fоr thе rating. Check wіth thе manufacturer оf уоur engines оr prospective engines tо sее whісh policy applies іn уоur case. Аnd bе surе tо аsk аbоut thе manufacturer’s preferred method fоr determining regular yacht maintenance intervals.
The VHF 200 provides full Class D Digital Selective Calling (DSC) capability via NMEA 0183 or NMEA 2000° connectivity. With up to 25 watts of transmit power at your fingertips, you’ll be able to stay in touch while on the water. The VHF 200 features a removable speaker microphone that allows the user to relocate the fist mic to a more accessible location on the boat, and a built-in 20 watt public address (hailer) system that can be connected to a hailer horn or external speaker. Also supports one wired GHS 10 handset microphone for full radio control from a remote location.
Video from the Garmin GC 10 can be viewed via onboard televisions, video monitors or compatible chartplotters that support video input. Whether you’re backing out of a boat-filled marina or keeping tabs on your engine room, you’ll have the information you need to make decisions while on the move. You won’t need to add separate hardware that’s device-specific to view your feed. There also are standard and reverse-image cameras to choose from. The reverse-image cameras reverse the video on your screen, perfect for backing out of tight locations. And with infrared functionality, you’ll be able to view your surroundings in low-light conditions.