HIGH PERFORMANCE BOATING AND YOU


Table of Contents

Safety........................................................... (1)
About This document..................................... (2)
Introduction to High Performance Boating...... (3)
Steering Forces......................................... ....(4)
The Motor.............. ..................................... (5)
Steering Systems ..... .................................... (8)
Propellers . . . . . . . . . . . . . . . ..................... . (9)
The Boat........... ..........................................(11)
Boat Equipment ........................................... (12)
Conclusion ....................................................(14)

(1) Safety 

This document contains certain information related to the personal safety of the operator, the passengers, and bystanders. Ignoring these safety issues will most likely cause injury. This document is an aid to understanding the operation of a high speed boat. It is not the only document about the subject that you should read before jumping behind the wheel of a high speed boat.

The continuing accuracy of this document cannot be guaranteed. All photographs and illustrations used in this document may not depict actual models or equipment and are intended as representative views for reference only.
Certain features or systems discussed in this document might not be found on all models.

(2) About This document 

This document will familiarize you with preparing and operating a high performance boat. A high performance boat requires top quality equipment in both design and manufacture. You should seek the help of an experienced high performance boater or expert in the field of racing when choosing accessory equipment for your boat and motor. Your local dealer may be knowledgeable in helping you with these choices or may be able to recommend an expert.

When your boat/motor/propeller combination has been fully assembled, have that same expert check out the installation of all equipment, its proper function and test it on the water. A person who has not been properly trained in the operation of a high performance boat should never attempt to drive such a boat at high speed. Never allow passengers or friends to drive your high performance boat unless they are experienced high performance boat drivers. Loss of control at high speed can occur suddenly and can result in persons being thrown from the boat. Accidents associated with high speed ejection can be serious, but the chances of injury can be substantially reduced by using the proper safety equipment.

(3) Introduction to High Performance Boating

The performance limits of a high performance boat should be approached gradually. Even if you have experience in another boat, this one will probably react differently and you will have to adapt your skills to this new boat/motor combination. Your first few hours of use should be at part throttle and without passengers in the boat. This is the time when you should learn the effects of changes in trim, throttle position and steering.

What Can Happen to a Boat at High Speed's

As any performance boat approaches its top speed, only a very small part of the boat bottom (called the "pad") is still in the water. Because of this, the driver must perform a very delicate "balancing act" to keep the boat under control. This task is easier in some boats than others depending mostly on the shape of the hull. Some of the forces which you will be balancing include:

* Wind forces on the front or side of the boat

* Buoyant forces pushing up on the bottom of the boat

* Drag forces on the bottom of the boat and against the motor's lower unit, propeller, and trim tab

* Thrust forces from the propeller

* Twisting forces caused mostly by the torque of the propeller in the water

* Proper motor trim angle

* Boat loading to keep an even keel

Because the relationship of all these forces is very complicated, it is important that you gain experience slowly. This means starting at slower speeds and gradually increasing boat speed while under the guidance of an expert. Instability, which happens whenever the many forces become unbalanced, will usually send little signals to the experienced driver. Because of this experience he can slow the boat, trim the motor slightly, or give the steering wheel a nudge which will again put the forces in balance. As speeds increase, the little signals of something about to go wrong will give you less and less time to make the corrective adjustment to prevent more serious instability from happening. It would be unwise for any high performance boater to go blasting off at high speed before he can recognize these signals and know instinctively what to do about them.

Before Leaving the Pier

Remove any loose equipment and put it ashore. If you need it on board, make sure it is securely tied down.

Make sure all hardware used to attach the motor to the boat is in place and tight. Do the same for all the hardware in the steering system. This is very important.

Check the operation of the emergency ignition shut-off switch. Start the motor, pull the lanyard and see that the motor stops. Make sure the lanyard is securely fastened to your life jacket.

On the Water

Before taking a new rig to wide open throttle, operate it at slower speeds. This is the time to learn how the boat reacts to the various inputs - both operator and naturally caused.

With the boat running at 30 to 40 MPH, operate the trim switch. Note how the boat reacts when you have trimmed to bow U P and bow DOWN - particularly in turns. Reset the trim for the flattest ride, circle around and cross your wake. While holding it in a turn, observe your boat's tendency to bounce or hook.

Next, check how the boat reacts to an emergency maneuver. Again, while running at about 40 MPH, and with plenty of open area, jerk the steering wheel quickly a half-turn with a quick return to straight ahead. The boat may roll from chine to chine, but should quickly smooth out so that you can feel in control. If it continues to china walk, it is an indication the motor is moving relative to the boat and is likely to be more severe at higher speeds. A recheck of the steering system for excess free play is in order.

Increasing Speed

Increase your speed gradually, as long as you feel you have things under control. Be aware that as speed increases, certain conditions affecting the boat's stability can appear. There are several kinds of instability, each can affect your control of the boat. If any of these conditions is allowed to go un-corrected, you could possibly lose control of the boat. These conditions are:

* Boat may pitch - Pitching is a rhythmic rising and falling of the bow of the boat. A pitching boat appears to be slapping the water. It's often called "porpoising." Some boats may pitch at low speeds, but this must disappear as the boat increases in speed. If pitching develops at high boat speed and corrections are not made to stop it, the bow of the boat might rise into the wind allowing the boat to blow over backwards or the boat's bow may plow into the water and go under or spin violently.


* Boat may roll - From the rear, a rolling boat would appear to flop from side to side. This rolling can also be described as "chine walking." At high speed very little of the boat's bottom is in the water. If the forces holding the boat upright on this small area become unbalanced, the boat may "fall off" sideways putting more of the boat bottom into the water. The water will then push the boat up and cause the boat to flop over on its other side. This rolling motion must be checked or the boat may start to "yaw" or catch the water sideways and flip over.

* Boat may yaw - The bow of a yawing boat will swing from side to side. Yawing often develops from an earlier unchecked chine walking condition. If a yawing condition is not corrected, steering control can be lost. The boat may flip over backwards, sideways, or catch its bow in the water and spin rapidly ejecting occupants.


(4) Steering Forces  

There are various steering forces that might be felt through the steering wheel on a mechanically steered rig. If your outboard is equipped with power steering, these forces are controlled by the power steering system. You will not feel external steering forces while the power steering system is functioning properly. If the power steering system is not functioning, operate at moderate speed until it can be repaired.

As the motor's propeller grabs and spins in the water, it causes twisting forces on the motor. These twisting forces or torque are felt as forces trying to twist the steering wheel out of the driver's hands. At high boat speeds the driver must put a correcting force on the steering wheel when the motor is trimmed up, to hold the motor's steering forces, even for a second or two, the driver must quickly relax the corrective force on the steering wheel or the boat will suddenly turn. Turning the boat at high speed is always very touchy so it is important that you know some of the things that can affect motor steering forces. Equipped with a right hand propeller, these forces are:

* Propeller blow out - Propeller "blow out" can affect the motor steering forces very suddenly. For a propeller to do its job, its blades must bite into undisturbed water. At some boat speeds, certain conditions of pressure and water flow may develop at the gearcase disrupting the smooth flow of water along its surface. Nearby air from the water's surface, or exhaust gases from behind the propeller, are pulled forward toward the sides of the gearcase. Suddenly the propeller blades and gearcase are surrounded by bubbles. Forward thrust and motor steering forces are gone. If you are correcting for external steering forces when "blow out" occurs, the boat could turn to the left suddenly.

* Ventilation - The trim angle of the motor or the location of the anti-ventilation plate of the motor with respect to the surface of the water can result in air from the water's surface being pulled into the propeller blade area. The propeller cannot grip this disturbed water and motor steering forces will drop suddenly.

Unlike propeller blow out, ventilation can occur at almost any speed but is most serious at high speed where the engine is trimmed out and the propeller is raised out of the water.

* Trim tab leaving the water - When the motor trim tab is correctly set, it helps you steer the boat by balancing some of the steering force. Without the tab, the driver would have to use greater effort at the steering wheel to hold the boat on course.

If you are holding the wheel against a steering force and the trim tab suddenly leaves the water, (for example when driving over the wake of another boat), you will feel a sudden change in forces at the steering wheel. The trim tab will no longer be helping you, and unless you anticipate this change in steering wheel force, the boat will naturally turn towards the left. Be aware that if you are running a high transom boat, the trim tab will usually be out of the water whenever the boat is on plane and the motor is trimmed UP, so all the steering forces will be felt at the wheel.

* Trimming the motor from full DOWN to full UP - When the motor is trimmed to full DOWN, the boat's bow will want to go deeper into the water. If the bow of the boat plows into the water, the boat may tend to bow steer or spin rapidly and eject the occupants.

When the motor is trimmed full DOWN you must exert a constant force to the steering wheel to keep the boat on a straight ahead path. As you trim the motor UP, the steering forces will become lighter, then the motor's steering torque will reverse and you will have to apply a force to the wheel in the opposite direction to keep the boat on a straight ahead path. If trimming is done at relatively high boat speed, the sudden steering torque reversals may cause a driver to lose control of the boat.

* Closing the throttle too fast - If you close the throttle suddenly while at high boat speed with the motor trimmed UP, the motor steering torque will stop abruptly. Since you were exerting a strong correcting force to the steering wheel against the earlier motor steering torque, the steering wheel could get away from you and put you into a hard turn which could be very dangerous. Unless there is some other reason to do so, always slow the boat gradually.

There are two conditions you should know about when stopping the boat.
One: a motor in trimmed UP position has less braking ability than a boat with its motor trimmed DOWN. When trimmed UP, you will need more room to come to a stop.

Two: if your boat is stern heavy, watch out for a following wave which will develop behind you as you come off plane. A following wave can break over the transom and spill into the boat.

The Motor

Safety Warning: Your dealer should install your motor and steering system. Improper motor installation could result in unexpected boat operation which could result in injury to the operator, passengers, or bystanders.

Complete the "break-in" procedure before running the motor at full throttle for an extended period of time. Refer to your Owner's Manual and Service Manual for the complete "break-in" procedure.

Steering Systems 

Safety Warning: Failure to use care in the selection and installation of remote steering system parts may contribute to steering system severance or jamming and sudden unexpected loss of boat control.

Safety Warning: If you use a "cable over pulley" steering system in conjunction with "racing" style steering arms,
the installation must not allow a significant change in cable tension when the engine is moved through its trim and tilt range. Loose steering cable could cause the system to jam or fail, resulting in unexpected loss of boat control.

The boat's steering system is important to the control of the boat and to the safety of the boat's occupants and others in the area. High performance boating requires special attention to the steering system to provide the highest degree of stability and control to the operator.

If your boat is equipped with a mechanical, push-pull cable system, all system components must meet or exceed the requirements outlined in ABYC Standard P-17. If your boat is equipped with a hydraulic system, the manufacturer or your dealer must verify that the system's capacity is sufficient for your application.

To complete the steering system, make sure you choose a large steering wheel with substantial finger grooves. At high speeds the driver will have to hold the wheel against forces trying to twist it out of his hands. Under some circumstances these forces change directions suddenly. Small wheels look nice but the smaller the wheel, the greater the effort required to overcome steering forces at the engine. Use the largest wheel that fits comfortably in your boat, and is recommended by the steering system manufacturer.

Once installed and connected, the system should be checked to ensure there is clearance between all steering system parts and the boat structure or other equipment in the transom area. Undetected interference can result in part breakage or weakening if the motor strikes an underwater object and tilts rapidly into the boat. Check by turning from lock to lock in both running and full tilt positions. Make sure all cable bends are not less than manufacturer's recommended minimum radius.

Safety Warning: Failure to check for interference may result in sudden, unexpected loss of boat control.

Keep the steering system manufacturer's installation instructions with your Owner's Manual. The instructions contain maintenance and testing information that is important for future reference.

Propellers 

When choosing a propeller for a high performance boat, the choice is really among the various stainless steel  propellers. While the aluminum propellers are good, their thicker blades are simply less efficient than the thin sectioned stainless steel propellers.

Note: When an aluminum propeller is replaced by a stainless steel propeller, the likelihood of drive-train breakage increases if you were to strike a submerged object.

The pitch of the optimum propeller for any particular sport boat can only be determined in on-the-water testing. Ultimately, you'll want the boat to run as fast as possible while staying within the motor's recommended full throttle operating range and while still providing acceptable all-around performance.

A quick look at the propeller selection guide included with your owner's kit will reveal a large choice of propeller sizes and types. The boat builder often has tested your rig with different propellers and often they will have a copy of the test results. Also check with others who are running similar rigs and see what style and size they are using, as your starting point.

Once a propeller style is chosen, you must run the boat to determine its operating characteristics. Items to check include:

* Engine operating RPM
* Boat speed
* Propeller ventilation
* Boat's plaining ability

Assuming engine RPM is within the full throttle operating range and there is little or no ventilation when trimmed for the best running attitude, most motors can be raised one notch using the adjustable stern brackets. Repeat the test run and note the effects on the operating characteristics listed above. If motor ventilation is still not excessive at best trim, raise the motor again and retest.

The objective of all these tests is to run at the upper end of the full throttle operating range using the highest transom setting possible without excessive ventilation and while retaining an acceptable ability to get onto plane and trim the boat. You will have to experiment with different height settings and propeller pitches to find the best combination for this particular rig. You may also reach a point where you can no longer operate with all the positive trim your boat needs for best speed. In this case, lower is better. Remember though, as you continue raising the motor, it is essential that you keep an eye on the water pressure gauge. If there is a drop in pressure at any particular motor height setting, you will have to drop back a notch or risk serious engine damage.

 

HPBoat-steer.gif (3540 bytes)

The Boat   

Safety Warning: Do not over-power your boat by choosing an engine that exceeds the horsepower indicated on the boat's capacity plate. Over-powering could result in loss of control. If the boat does not have a capacity plate, see your dealer or manufacturer.

You must choose your boat. Since it is a performance rig, you will probably choose a boat with a horsepower capacity that matches your engine. Remember, if you try to over-power your boat, you might end up with a rig that is dangerously hard to control.

Regardless of type, the performance boat you choose should have a minimum of wetted surface (A), when running at full speed. Generally speaking, the less wetted running surface, the faster you will go.

FIG.1) A "V" bottom pad boat will give you good all-around performance. High performance "V" bottom pad boats usually incorporate a stepped transom (B). FIG.2)  The stepped transom allows you to mount the engine higher. A higher transom height reduces the amount of gearcase in the water and improves boat performance. Watch your engine water pressure when experimenting with engine height!

FIG. 3) A modified tunnel design gives you high performance and good stability in rough water. It gives you some of the qualities both the "V" bottom and tunnel designs.

FIG.4) The sport tunnel is an adaptation of a racing design and is generally the fastest of all on smooth water. Once on plane, the tunnel design traps air which lifts the boat out of the water. The sport tunnel skims across the water rather than slicing through it. This hull design requires a skilled driver! The tunnel's air cushion makes the boat very sensitive to water conditions, changes in speed, turns, and changes in wind direction.

Boat Equipment 

REMOTE CONTROL - The remote control shipped with your engine is designed specifically for your  outboard. In most cases, the control incorporates start-in-neutral protection and an emergency ignition cut-off switch. The emergency ignition cut-off switch can prevent a runaway boat situation by stopping the engine's ignition if the driver leaves the operator's position unexpectedly.

Safety Warning: If you choose an alternate remote control, it must have start-in-neutral protection. This feature can vent injury resulting from unexpected motor operation. The emergency cut-off switch must also be installed in the circuit.

INSTRUMENTATION - To monitor boat performance you should consider an accurate tachometer, an extended range speedometer, and an engine trim indicator gauge. The tachometer will show you that the engine is always within the RPM operating range specified in your Owner's Manual. The speedometer will demonstrate speed changes caused by changes in engine height, propellers, and engine trim angle.

The engine trim indicator gauge allows the driver to reset the engine at a predetermined angle for optimum performance.

A 0-30 PSI engine water pressure gauge will allow you to monitor changes in the engine's cooling system. The engine water pressure gauge can provide an early warning of cooling problems caused by changes in engine height or trim angle.

SEATING

When the driver is held firmly in place by a good seat, he can concentrate on controlling the boat! Your high performance boat should be equipped with a wraparound or bucket driver's seat. Also consider a solid footrest for your left foot to help hold you in place when the boat bounces.

Passenger seating should be similar and should be complemented by a handhold to help keep them in place.

FOOT THROTTLE

Another way to improve boat control is to keep both hands on the steering wheel at all times. A racing
style foot throttle can be installed to handle engine speed settings. A lot of high performance boaters also put the trim switches on the footrest or steering wheel. Again, boat control is improved because you don't have to remove your hands from the steering wheel to change engine trim settings.

FUEL SYSTEM

Your boat's fuel system must be carefully designed to provide adequate fuel flow for your high performance engine. Attention must be paid to fuel line diameters, connections, components, and system length. When assembled, the boat fuel system must be tested for fuel flow and restrictions. These tests are outlined in your engine's Service Manual.

A water separating remote fuel filter, is an important part of any boat fuel system. Some are designed specifically for two cycle applications. It can separate contaminants and moisture from the fuel supply without causing a significant pressure drop in the system.

As a performance consideration, the fuel tank should be located as close to the transom as practical. This will reduce the hull's wetted running surface and should increase top speed.

BATTERY

The engine's battery must be of heavy-duty construction and ample capacity. For larger engines, look for a
capacity of at least 500 CCA at 0o F with a 99 minute reserve at 80o F. Maintenance-free marine batteries can be used with larger engines equipped with fully regulated charging systems. Check the specific requirements of your engine outlined in your Owner's Manual or Service Manual.

Be sure the battery is installed in a vented container and that it is securely fastened to the boat. The use a cheap plastic battery tie downs in a high speed boat is more than a danger to the battery. Replace any plastic or light gauge battery tie downs with high performance or racing style tie downs. The less your battery moves, the less chance of loose connections and failure.

Conclusion 

High performance boating requires the driver to give a high degree of attention to driving. Somewhere out there ahead of the boat there are always different wind currents, wakes from other boats, and debris floating low in the water. When you are moving fast almost any disturbance in the water can cause the boat to roll or yaw, requiring the proper corrective action. The faster you go the quicker things will happen. Only you can decide when you are going fast enough.

High performance boating is an exciting, exhilarating sport. The sport boater must, however, be considerate of others who may use the same waters. High performance boating requires a lot of water. Pursue your sport where you have plenty of room and your noise and wake won't annoy others. Make sure your pursuit of pleasure does not create a hazard or annoyance to nearby homeowners, fishermen, swimmers, water skiers, sailors or other powerboats. Make common sense and courtesy a regular part of your boating routine.

OMC Second Effort High Performance Division

HPBoats.gif (8925 bytes)
Home Page   |   Returned Mail   |   Odds n Ends  |  Boat Builders  |  Engine Page  |  Electric Page  |  News Page  |  Safety page  |  Trailering  |  More About Us   |   Related Sites   |   Special offers   |   Event Calendar   |   Opportunities  |  Tools  |  Mailbag  |