Chapter 3: Outboard Systems
Selecting Essential Systems and Components
Even so, buyers often face choices in steering systems, controls and instrumentation. Take the time to study your options and choose the setup that best suits your boating needs.
Many small outboards are sold without instrumentation; others feature at least basic gauges. The most vital is a tachometer, which measures engine rpm and shows how hard an outboard is working. No matter how many gauges your boat is equipped with, you'll find yourself glancing at the tach most often. In fact, you'll come to rely on it the same way you rely on your car's speedometer.
Speaking of speedometers, although pitot-tube speedos are notoriously inaccurate, they show changes in boat speed and thus are useful for measuring prop performance and other parameters when "setting up" a boat for top performance.
We highly recommend a temperature gauge. Although many outboards are equipped with buzzers or "idiot" lights that signal when the engine is overheating, such a potentially catastrophic condition is best headed off at the pass. A water pressure gauge can be even more helpful since it indicates the volume of cooling water passing through the engine. Because it responds faster than a temperature gauge, it's often a better indicator of the condition of the cooling system. (More on this in Chapter 4.) A fuel gauge is also useful, but knowing how your particular gauge responds is essential.
Smart Instruments
Outboard instrumentation is currently undergoing a sea-change, as advances in digital technology are bringing about exciting breakthroughs. Chief among these is the Motorola 555 microprocessor that's becoming standard on an increasing number of Mercury outboards. When combined with Mercury's digital SmartCraft instrumentation, it not only monitors the engine, but also keeps tabs on boat functions - including fuel management. This is true digital instrumentation (not simply LED readouts on analog gauges). From a boatrigger's perspective, the system greatly simplifies wiring. From a boatowner's perspective, it allows faster troubleshooting and makes it easier to add gauges and new functions later.
Changes are also taking place in engine controls. Most outboards are packaged with a side-mount control that includes the key switch, choke and electrical harness, as well as shift and throttle functions that are mechanically actuated via push-pull cables. The next step up is a dash-mount or binnacle-style control box. By separating much of the wiring harness from the shift and throttle functions, they allow for a dash-mounted key switch. They also place shift and throttle cables under the console or behind the side panel for a neater installation.
The latest innovations are "fly-by-wire" systems that replace mechanical shift and throttle cables with wires. Recently introduced on some Mercury V6 outboards, the Digital Throttle & Shift (DTS) system's shift and throttle functions are controlled by a rheostat at the control box and "stepper motors" at the engine. Besides being easier to install, the system eliminates problems with binding cables and allows for engine installation in tighter quarters, creating more room at the transom.
Steering your right
Steering systems have greatly improved over the past several years. Although the push-pull cable is still common, hydraulic steering is becoming increasingly popular in heavy-duty and high-performance applications.
Cable steering is available for two types of helms: rack-and-pinion and rotary. Rack-and-pinion helms generally provide the easiest steering, as there is less friction compared to rotary helms. The downside is that these require considerable room behind the dash to mount. Rotary helms are more compact.
A steering system should be chosen based on the stress it will be subject to. This varies according to the boat, its setup, engine trim, propeller and other factors. The rule of thumb is that single-cable steering is satisfactory for outboards up to 130hp. More powerful engines should be equipped with dual-cable steering - which we consider the minimum for a V6 outboard mounted on a high-performance boat. Dual-cable steering stacks two helms on the same steering wheel shaft, and distributes the load across two cables extending back to the engine. By placing one cable under tension and the other in compression, steering "slop" is minimised. Many high-performance drivers believe this system provides the best "feel" and control.
Hydraulic steering is being installed on more boats every year, and the latest systems for high-performance outboards are so refined that steering lag at the helm is nearly imperceptible. This is important when trying to balance an ultra-fast V-hull on its pad. On offshore boats and cruising hulls, hydraulic steering has become almost universal. Its main advantages are that it prevents steering-torque feedback at the helm, and its stainless components provide excellent corrosion resistance. The most recent twist in hydraulic steering is less expensive systems designed for smaller boats. Hydraulic steering on outboards of 50hp or less may be common in the near future.
Choosing your outboard's systems wisely can increase your boating pleasure, and adding a few key upgrades will help you get the most from your investment.
Your Guide to Outboards