Twin engine Boat Handling

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For many people, moving from a single engine to a twin engined vessel is a big step. If you are used to an outboard or inboard-outboard, it will take a mental shift when learning twin engines with shaft drive.

The first difference you will notice is that operating astern propulsion is not as effective as on vessels with legs. The rudder is not effective when going astern until you have the boat moving and water flowing across the rudder.

Rule 1 for beginners:
Neutral is your best friend - especially as the size and weight of the vessel increases it is important to keep the speed of the vessel at the minimum required to retain control. Speed is your enemy and when you go into gear only stay in gear 1 - 2 seconds. This will prevent the vessel from gathering speed which gives you less time to react and think. Usually the objective is to coast the vessel to its berth. When you have 65,000 lbs. under you, that is a lot of momentum.

Rule 2
To start we will have our engines at idle and the rudders centered. Mostly we will use only the gear levers to steer the boat. There are a number of memory aids to assist you in operating the controls.
1. Pretend the two gear levers are the handlebars of a bicycle. If you want to turn to port, move the gear levers the same as you would with a bike. In this case Starboard engine forward and Port engine astern.

2. Stand at the helm and grasp the gear levers, one in each hand. If you lock your elbows and simply rotate your upper body so you are facing the direction you want the boat to move, you automatically move the correct lever in the correct direction.

3. Imagine parentheses(curved brackets) alongside the gear levers. For example, if we use o to represent the gear levers and the parentheses would indicate the direction the boat would move.
(o o) If we move the port lever forward, the boat would move forward and the bow would turn to starboard.

Most of the time when docking or undocking you would have your rudders centered and the engines at idle. You handle the boat by moving only the gear levers.
To execute a slow turn to starboard, you would move the port gear lever forward. To make the turn tighter, you would move the starboard lever astern(reverse).

For further information on many aspects of boat handling, visit our E-lessons page.

Nearly all twin inboard engined vessels have the transmissions set so the propellers are turning outwards when operating ahead, in forward gear. When looking from the stern towards the bow the Starboard prop will rotate clockwise, Right hand, and the Port propeller will rotate counterclockwise, Left hand.

Because the prop shaft is angled there is a sideways thrust which is most noticeable when you go astern. This is called P-effect or commonly called prop-walk. If you consider the prop as a wheel at the stern, when the port prop operates astern and rotates clockwise, it will move the stern of the vessel to Starboard. Because the propeller is off-center it generates a twisting motion to the vessel which also moves the stern to Starboard.

If we wish to dock starboard side to the dock, we will approach at a shallow angle. We want the boat to coast up to the dock so we use neutral to control our speed. Just before you think that the hull is about to hit the dock, put the port engine astern briefly. The boat should stop, the bow swings out and the stern swings up to the wharf.

Points to remember:
1. Rudders amidship, centered
2. Engines at idle
3. Control your speed by using neutral. Around the marina or near other vessels, neutral is your best friend.
4. Steer the vessel by using the gear levers only. (See the above notes) For those people who have experience driving skid steer loaders or army tanks, you have an advantage.

Required navigational equipment is a little different for large and small powerboats but all marine navigation is dependent upon knowing these five things:
Ø Direction
Ø Speed
Ø Time
Ø Distance and
Ø Depth.
Since you need to know these five things, you require navigational gear that will give accurate information about all five of them regardless of the size of boat.

A compass is a necessity and we aren't discussing one of those freebies that come in breakfast cereal. You need a big and steady compass that can be easily read even in adverse weather conditions. A compass gives direction which is the first information that you need for navigation.

If you wear a digital watch (water proof and shock proof,) and one with a stop watch function, you can determine the next three pieces of required information for navigation. If you know any two of the next three factors (speed, time and distance) the third can be easily calculated using the Sixty D Street formula covered in the Home Study Coastal Navigation Course .

Essentially you can cover 4 of the 5 required pieces of navigational information with a compass, a digital watch and a knotmeter which will give you speed and distance travelled.

A simple depth finder can cover the 5th requirement but if you can, find and buy a good GPS/Chart Plotter/Depth Sounder unit. These units aren't all that inexpensive but when you consider the value of human life they aren't all that expensive either.

You should always carry paper charts covering your planned route. As anyone who operates a personal computers knows all too well, electronics can breakdown and it's always at the worst possible moment. A compass and a paper chart will still be there even if the entire electrical system on your powerboat fails.

Many beginners have difficulty when they first try to back their boat into a slip. Looking over your shoulder and then trying to remember which way to move the gear levers can be confusing. One technique, if your helm will allow you, is to stand up and face the stern. Reach behind your back and handle the gear levers. By facing the stern, the gear levers will move the boat in the same direction it would if you were facing forward.

Another point to remember is that the pivot point of the vessel shifts when you are moving astern. When moving forward, the pivot point is aft of the bow. When moving astern, the pivot point is forward of the stern.

Up to this point, we have left the rudders centered. By turning your wheel in the direction of the turn, you can have the vessel turning quicker. For a turn to port:
1. Put your wheel hard to port,
2. Starboard engine ahead and port engine astern.

For a turn to starboard you would reverse the wheel and engines.

Sometime when backing into a slip, the wind will push you away from the float so you crew is unable to step ashore with the stern line. If the float were on your starboard side and you are a couple of feet off the float, a technique is to use the wheel. Put your wheel away from the float, in this case to port, and then go ahead on the dockside, starboard engine. The stern will swing toward the float. To stop the forward motion, you could place the port engine astern at the same time.

Sometimes you need to move a boat sideways and you do not have bow and stern thrusters.

There are a number of ways to accomplish this maneuver. This is one way I have taught and used successfully on vessel ranging from Bayliner 3818 to Ferretti 55.

Assume you wish to dock on your starboard side and your boat is10 feet away and parallel to the dock. Put your wheel hard to port and momentarily place the starboard engine in forward and the port engine in reverse. Because of the rudders, the stern will take a large swing to starboard, towards the dock. Both engines to neutral and then starboard in reverse and port forward. What you are accomplishing is to bring the bow back in line with the stern and parallel to the dock. Shift to neutral on both engines and repeat the sequence. The boat will move to starboard and towards the dock.

You may need to adjust the amount of time you stay in gear on each engine so the boat does not move forward or aft. When you have the rhythm correct, the boat will slide nicely sideways.

Always remember to place your rudders in the direction opposite the way you want the boat to move