Tracing wiring runs in boats can be a painful task. Wire is often run in concealed areas, and at the ends, where it is visible, it’s usually bundled with a bunch of other wires. The good news is that most boatbuilders use the American Boat and Yacht Council color codes for boat wiring. Specific colors are used for specific equipment. Knowing these colors makes troubleshooting electrical systems easier.


Black Ground Negative / Neutral Main Return
Blue-Stripe Tilt up and or trim out Tilt and or trim circuits
Brown Alternator Charge Light Generator Terminal or Alternator Auxiliary Terminal to Regulator
Generator Armature Generator Armature to Regulator
Pumps Circuit Breaker or Switch to Pumps
Brown w/Yellow Bilge Blowers Circuit Breaker or Switch to Blower
Dark Blue Cabin & Instrument Circuit Breaker or Switch to Lights
Green or Green w/Yellow Stripe Bonding System Grounding Wires (if insulated)
Green Stripe Tilt down and/or trim in Tilt and or trim circuits
Grey Navigation Lights Circuit Breaker or Switch to Lights
Tachometer Tachometer Sender to Gauge
Lt. Blue Oil Pressure Oil Pressure Sender to Gauge
Orange Accessory Feed Ammeter to Alternator or Generator
Common Feed Distribution Panel to Accessory Switch
Feed Accessory Circuit Breakers or Switches
Pink Fuel Gauge Fuel Gauge Sender to Gauge
Purple Ignition Ignition Switch to Coil & Electrical Instrument
Instrument Feed Distribution Panel Electrical Instruments
Red Instrument Feed Distribution Panel to Electrical Instruments
Power Feeds Positive Main Power (particularly un-fused)
Tan Water temperature Water temperature sender to gauge
Yellow Generator Field Generator to Regulator Field Terminal
Ground Negative / Neutral Main Return
Yellow w/Red Starting Circuit Starting Switch to Solenoid


Wire / Conductor Sizes

Length (feet): Determined by measuring the length of the wire from the positive (+) power source connection to the electrical device and back to the negative (-) power source connection.  Note that the power source connection may be the battery, panel-board or switchboard.

Current (amps): Determined by adding the total amps on a circuit.

Wire sizes not covered in Table C or Table D may be calculated by using the following formula:

After calculating the Circular Mil Area (CM), use Table B to determine the proper conductor size.  The National Fire Protection Agency and Coast Guard require that the next larger conductor be used when the calculated CM area falls between two conductor sizes.

CM=K x l x L / E

CM = Circular Mil area of Conductors

K = 10.75 (Constant representing the mil-foot resistance of copper)

I = Current – amps

L = Length – feet

E = Voltage drop at load (in volts)

For Example…

Q.  A bilge pump draws 10 amps.  The positive run is 11 feet from the power panel, including the float switch.  The negative run is only 10 feet.  What size wire?

A.  Use the following formula to reach the correct answer:

CM = 10.75 x 10 (amps) x 21 (total length of run) / 0.36 (3% of 12v) = 6,271

The table below shows that 12 AWG wire has a CM area of 6,500 and is the correct choice. However, SAE wire has a CM area of only 5,833.  Under NFPA and USCG regulations, 10 SAE wire must be used.

CM = 10.75 x 10 (amps) x 21 (total length of run) / 0.96 (3% of 32v) = 2,352

Ampacity is the ultimate safe current carrying capacity of the wire before damage occurs to the insulation, without regard to voltage drop.  Because the insulation of most SAE wire types is not the same as ANCOR, this chart should not be used for other conductor types.  Use Table C & D to find proper wire size to insure adequate performance.

AWG Sq. mm AWG CM area SAE CM Area Ampacity Engine Space
Outside Inside
18 0.8 1,600 1,537 20 17
16 1 2,600 2,336 25 21
14 2 4,100 3,702 35 30
12 3 6,500 5,833 45 38
10 5 10,500 9,343 60 51
8 8 16,800 14,810 80 68
6 13 26,600 24,538 120 102
4 19 42,000 37,360 160 130
2 32 66,500 62,450 210 178
1 40 83,690 77,790 245 208
1/0 50 105,600 98,980 285 242
2/0 62 133,100 125,100 330 280
3/0 81 167,800 158,600 385 327
4/0 103 211,600 205,500 445 378


Volvo IPS Joystick Control: Simple Captaining for New Boats

We get asked a lot whether new yacht owners will be comfortable piloting larger personal vessels (45ft+) by themselves, and without a captain. Although older vessels require quite a bit of skill and technique when it comes to close-range piloting, the newer yachts with either the Axius (Mercruiser) or IPS system (Volvo) allow for ease of use by any pilot, from the veteran sea-goer to newly-christened waterman. I’d venture to say, even a teenager with gaming skills could pilot a 50ft yacht like a pro- no experience necessary. The close-range piloting is no longer fighting single or twin screw transmissions; it’s far more intuitive and natural.boat-photo-volvo-ips-joy-stick

The joystick is perhaps the most well-known feature of Volvo Penta IPS, making it possible to dock in a new and completely intuitive way. Since its release it has been accompanied by many other smart features, such as Dynamic Positioning System and Sportfish mode. The latest generation of Volvo Penta controls has integrated buttons for Low-speed mode, Single-lever mode and Cruise control, making it even easier to enjoy boating with Volvo Penta IPS.

See more at: Volvo Penta IPS

There’s little difference between Mercruiser’s Zeus pods and the Volvo IPS pods… except that Volvo’s support for mechanical issues might help you gear toward their IPS systems.


Surface Drives: Props halfway out of the water? 1 Word: Efficiency

When most people hear the term surface drive, they think speed and high performance, but what these rather specialized propulsion units are really about is efficiency. Because the propeller blades break the water’s surface — they are called surface-piercing propellers — the engines powering them run under less load than with fully submerged props. Half of the propeller spins in the water. The other half rotates above the surface. This lets the boat make better use of the power of its engines and go faster than one with submerged props. (BoatingMag)

Check out this video of Surface Drives in action:

The engineering for this technology has been attributed to two independent inventors/innovators/enthusiasts: the late Renato ‘Sonny’ Levi and Howard M. Arneson. Sonny Levi had pioneered and developed his surface drive technologies in Malaysia, while Arneson followed for ultimate performance with a larger budget in California. You can find Arneson surface drives on the market today.


The surface piercing or ventilated propeller is a propeller that is designed to intentionally cleave the water and entrain atmospheric air to fill the void, which means that the resulting gas layer surrounding the propeller blade consists of air instead of water vapour. Less energy is thus used, and the surface piercing propeller generally enjoys lower drag than the supercavitating propeller. The surface piercing propeller also has wedge shaped blades, and propellers may be designed that can operate in both supercavitating and surface piercing mode. (Wiki)

The Arneson Surface Drives are among the most efficient marine propulsion systems in the world. Their surface-piercing propeller design reduces underwater drag by 50% compared to conventional submerged propeller drive systems. The only surfaces to contact the water are propeller blades and a protective skeg. This results in higher overall speed, quicker acceleration, and a better payload to power ratio… AND… 50% less drag significantly improves fuel economy while lowering operating costs.

For work, pleasure, gas, diesel, or turbine power systems capable of torque outputs exceeding 30,000 ft. pounds, the Arneson Surface Drives come in ten model sizes and various configurations for each model. Available in, Aluminum or bronze castings, straight or drop-center models, 12 or 24 volt compatible systems, plus the new Arneson Dual-Fin surface drives available in the ASD8 and ASD10 models.

Comparisons-1(Photo credit: Arneson Industries)

Advantages of the surface drive by Arneson:

  • 15% to 30% speed increase over conventional systems.
  • 15% to 30% increase in fuel efficiency.
  • More efficient than I/O’s
  • Corrosion resistant
  • Size adaptability, from 100 hp to over 10,000 hp applications.
  • Low maintenance requirements.
  • Ability to adjust propeller submergence while underway.
  • Ability to adjust submergence to match horsepower output permits conversion of more thrust as appropriately needed.
  • Propellers ventilate to the surface rather than cavitate under the hull reducing noise and destructive hull and prop erosion.
  • Flexibility in engine installation location.
  • Less Vibration than Inboard or I/O applications
  • Shallow water operation (elimination of underwater appendages).
  • Accessible propeller servicing.
  • Steerage by the positive thrust of the propeller and not by the propeller thrust to the rudder. This is equivalent to sports car rack-and-pinion steering performance.
  • For all it’s sophisticated performance, it is a less mechanically complex and fragile design than other propulsion systems.
  • Most models are available in Magnesium Bronze or Aluminum.
  • No limitations to shaft angle, blade top clearance, draft to restrict selection of optimum diameter propeller.
  • Adaptable to a wide range of engine applications, whether gas, diesel, or turbine.

It might come as a surprise that a boat doesn’t necessarily need to be designed for surface drives. A V-bottom would need some rocker to generate bow lift because surface drives don’t create any, but a bottom designed for straight inboards or sterndrives can see performance and efficiency gains with surface drives. Among the first performance V-bottoms to break the 100 mph mark was a nonstepped Hustler 32 powered by 630 hp engines and Arneson drives.

The biggest downsides to surface drives are that they make docking more challenging because they lack the blade surface of a submerged prop and that they extend well aft of the hull, sticking out like appendages. But when you’re in search of speed and efficiency, looks aren’t everything. (BoatingMag)



Skyhook – Your “Electronic Anchor” from MerCruiser – Dynamic Positioning

As a Captain and Marine Surveyor, I’ve had the pleasure to captain quite a few boats with this new technology, and I approve! The Axius joystick system is great for close-range piloting, and makes the job of parking in slips quite simple. Skyhook is an extension of that system, allowing the Axius-enabled drives to maintain a solid position while you’re fishing or just out at sea.

If you’re thinking about purchasing a boat with the new joystick technology, give us a call! I can help you to understand your systems as I survey your yacht.


Keep your boat in place with the push of a button!

Mercury Skyhook digital anchor allows you to lock your boat’s position using a GPS satellite antenna. Then, working with your engines and drives, Skyhook maintains your position and heading regardless of wind or current.

Key features

• Ideal for holding the boat over a fishing spot, waiting for bridges to open or holding position while next in line at a fuel docking station.

• GPS technology and electronic compass automatically control shifting, throttling and steering to maintain heading and approximate position.

• Simple to operate – just place the levers in neutral and push the Skyhook button to lock position and heading.

• Standard on Zeus and Joystick Pilotingequipped boats. Available on Axius boats with Premier Package.


Source: Mercury Marine

Hybrid Propulsion Technology (Yachting Magazine)

A word that pops up with increasing frequency in the world of marine propulsion is hybrid, and for good reason. The technology offers advantages over traditional diesel-only drives in some scenarios, on both yachts and commercial vessels.

Whether it is right for you depends on a number of factors, but before deciding, it’s necessary to understand what a hybrid system is and how it operates. Let’s start with an explanation of a total electric vessel, in which an electric motor drives the propeller shaft and the power for the motor comes from an electrical storage device.

Today, these storage devices are usually batteries, but research is active on other solutions such as supercondensers.

Such vessels usually have a limited range and are recharged from dockside outlets, but wind-driven generators and solar panels can provide underway charging. Also, some experimental sailboat installations use the propeller to drive a small charging generator when operating solely under sail.

The 100-plus-year-old, diesel-electric (or gasoline-electric) propulsion system has reliably powered everything from locomotives to transit buses to submarines to yachts. One of the largest diesel-electric vessels is the16-year-old, Lürssen-built, 315-foot Limitless. In a diesel-electric installation, a diesel engine drives a generator, much like an ordinary auxiliary generator set.

The generator powers an electric motor connected to the propeller shaft. Larger yachts add more engines, more generators and more motors, with an increasingly complicated switching and control system. On superyachts such as Limitless, the in-port hotel loads such as lighting, heating, cooling, cooking and guest accommodation support can rival the propulsion loads at sea, so using one power system for both situations can be a smart decision.

A hybrid propulsion system is basically a diesel-electric system with the addition of electrical storage devices and enhanced controls. Thus, each hybrid system involves an electric motor, a generator, electrical storage devices, a means to charge them and a control system. It also involves an engine, usually fueled by gasoline or diesel but increasingly by cleaner-burning liquefied natural gas (LNG) for commercial fleets.

There are two main types of marine-hybrid systems: serial and parallel. In a serial system, the electric motor drives the propeller shaft directly, just like on a total electric vessel. The engine, which has no direct connection to the propeller shaft, drives the generator both to charge the batteries and to power the electric motor. The batteries power the electric motor when the engine isn’t running, and the controls keep the whole system working.

In a parallel setup, the engine is connected to the propeller shaft through a combination motor/generator and a clutching system. The engine can drive the propeller directly without the motor being active, or the motor can drive the shaft with power coming from batteries or the auxiliary generators while the main engine is shut down.

In addition, the main engine can charge the batteries via the motor/generator when it is also propelling the vessel, but its full power is not required for propulsion. It’s a bit more complicated than a serial system, but is more flexible and delivers more overall efficiency.

It is for these reasons that parallel hybrids seem to be gaining in popularity over serial hybrids as the necessary specialty equipment becomes increasingly available. Now, a hybrid marine propulsion system is not the same one as on a hybrid car, although the technology and equipment are similar. The difference is how it operates.

The raison d’être for a hybrid car, pure and simple, is enhanced fuel efficiency. It recaptures the energy that would otherwise be lost in idling at intersections and traffic jams, in braking, in coasting downhill and in constantly varying speed on the highway.

These conditions don’t exist in marine applications, so we must look for other reasons why hybrid propulsion makes sense. For commercial service, where design decisions are largely driven by pure economics, there are increasing numbers of hybrid vessels.

The reasons come from duty cycles on, for example, supply and support vessels for the offshore oil industry and tugboats for harbor service. These spend large amounts of time idling or standing by, more time actively maneuvering, and little time simply cruising.

Additionally, some commercial vessels such as sightseeing and dinner-cruise craft benefit from the elimination of diesel-engine noise, and when they operate in environmentally sensitive areas, the absence of exhaust gas is a plus.


While hybrid systems make perfect sense in some commercial applications, the picture is less clear regarding yachts. Several yacht builders have occasionally offered hybrid options with mixed results. Ferretti Yachts built a 74-foot Mochi Craft long-range hybrid, a lovely yacht that I had the opportunity to examine in detail with the builder’s engineers in 2008.

The technology was unassailable and the construction was exemplary, but the price premium was about a third above the diesel-only version. It was apparently too much for even the most green-minded shoppers, especially as the yacht’s introduction coincided with the beginning of the worst recession the boating industry has seen. One wonders, though, if such a yacht might succeed better today when the greater availability of equipment would help bring the price down.

Royal Huisman delivered the 190-foot sailing yacht Ethereal in 2009, a masterpiece of both hybrid technology and overall environmental awareness. She utilizes two 300 kW ­Combimac electric motors for silent running. (The boat also features twin 714 hp Caterpillar C18 diesels.) Only one engine is required to move this 190-footer along at cruise speed, and the propulsion system also charges her main battery bank.

Those electric motors work in concert with silent thrusters for ­station-keeping, giving swimmers fume-free bathing too. Custom-designed and built for tech guru Bill Joy, she’s a floating test bed for a host of his innovative ideas, as much a research vessel as a personal yacht.

Royal Huisman continues to incorporate some of the technology developed on Ethereal in its current builds, but none has duplicated the complete package found aboard Joy’s yacht.

On the other hand, Elco Motor Yachts has seen a rebirth of its company based largely on electric and hybrid craft. And David Marlow, head of Marlow Marine, is nobody’s dummy when it comes to delivering what customers want.

He added solar-power options to his company’s line of Explorer motoryachts, which range in length from 53 to 97 feet, and offers an electric-propulsion option for the Marlow-Hunter 27 sailboat, so I suspect a hybrid option would not be out of the question should a customer ask.

Greenline, which offers 33-, 40- and 48-foot production powerboats, is perhaps the most successful with the hybrid concept to date. The builder is reportedly working on 55- and 70-foot models. In a written statement, Greenline cites environmental friendliness as the main advantage of its yachts:

“We want to keep our most beautiful boating spots in the same pristine condition as when we first discovered them. We want to enjoy the untouched beauties of the boating world for years to come and pass them on to our children and grandchildren.”

Not only do the boats employ hybrid-propulsion systems, but they also include solar panels on the house top and other “green” measures to optimize efficiency.


Interestingly, just before the recession, when both the Mochi Craft and Ethereal first saw the light of day, many ­builders were gaining interest in hybrid-system potential.

The level of activity was such that the American Boat and Yacht Council saw fit to update its technical standard TE-30, “Electric Propulsion Systems.” While the standard does not address hybrid systems specifically, its guidelines on electrical safety should be adhered to by anyone involved in such systems.

Even in those heady pre-recession days, however, in-depth research would have been too expensive and time-consuming for any single company, so an international, multimillion-dollar effort was mounted. Under the auspices of the International Council of Marine Industry Associations, and with the cooperation and support of a host of electrical- and hybrid-equipment suppliers, a research program dubbed HyMar (for Hybrid Marine) was undertaken specifically to study the technology, the environmental reality and the economics of hybrid marine propulsion systems.

On the research team was Nigel ­Calder, sailor and author of the well-respected Boatowner’s Mechanical and Electrical Manual, and it was his Malo 46 sailing yacht that became the test bed.

In support of meeting clean-air treaties and reducing emissions from marine sources, one of the project’s stated objectives was “reduction of total fuel consumption by 30 percent relative to conventional diesel drive, tending to 90 percent on long-distance sailing boats.”

The HyMar report concludes that “hybrid systems are capable of delivering higher fuel efficiency for propulsion on a cruising duty cycle,” but the reported savings are nowhere near the initial hopes. The report goes on to state, “It is unlikely that hybrid systems will demonstrate enough savings in terms of fuel costs to justify the higher capital costs.” It admits, with surprising candor, that “energy efficiency is more complex than appears at first sight!” In other words, a well-designed hybrid system can offer a number of operational and environmental benefits, and may even be more fuel-efficient than a diesel system in some applications, but most yacht owners will never see an economic payback, and some will see no savings at all.

Those thoughts were echoed by Marnix Hoekstra, naval architect and co-owner of Vripack, one of the world’s largest and most respected yacht design firms, when I spoke to him at the recent Monaco Yacht Show. He strongly supported hybrid systems for use in yachts, much like in commercial vessels, when special operational requirements or desires dictate a need.

He also was quick to point out that most yachts aren’t taking advantage of other measures, such as better hull forms and more sophisticated propellers, that should be implemented before considering hybrid propulsion as an energy-conservation measure.

With a smile, Hoekstra concluded, “If an owner wants to be totally green, he should not build a yacht at all. Short of that, though, there are many things that can be done to improve the impact on the environment. Hybrid drive is only one of them.”

Read More: Yachting Magazine