MARINA OIC-NW Theoretical Exam common mistakes
MARINA OIC-NW Theoretical Exam · Understand the traps and how to avoid them.
When a COLREGs question describes two power-driven vessels in a crossing situation, the candidate applies the give-way/stand-on rule using the bearing at which the other vessel is first noticed, without re-checking whether the bearing is actually drawing aft or forward as the vessels close.
Candidates memorize 'the vessel with the other on her starboard side is give-way' as a fixed picture rather than as a test of relative bearing change. Under exam time pressure they anchor on the first drawn bearing and skip the dynamic check that distinguishes crossing from overtaking and confirms risk of collision exists.
What to do instead
Before answering, state the two bearings overtly: write down the other vessel's relative bearing at first sight and again a short interval later, and state whether it is constant (risk of collision, crossing rules apply), drawing aft (you are overtaking, Rule 13 applies and overrides Part B Section II), or drawing forward (you are being overtaken). Only then assign give-way/stand-on and the required action. Practise 20 short crossing/overtaking/head-on scenarios until the bearing-change test is automatic.
On lights and shapes questions, the candidate answers with the correct light colours but the wrong arc, range, or vertical/ horizontal positioning, for example placing the anchor ball forward instead of where it belongs, or confusing the two all-round red lights vertically in line for a vessel not under command with the three all-round red lights of a vessel constrained by her draught.
Lights and shapes are learned as colour lists rather than as spatial diagrams. Candidates recall 'red over red' without holding the geometry (which mast, what vertical separation, what arc each light shows, whether shapes go forward or where best seen) and the exam deliberately tests the geometry, not just the colour.
What to do instead
Redraw each vessel type from memory as a side-profile sketch showing every light's arc, colour, position and vertical order, plus the day shapes in the same sketch. Do this for power-driven underway, sailing, NUC, RAM, constrained by draught, fishing, trawling, minesweeping, towing, and anchored/aground. Compare against the rule text and correct the sketch; repeat weekly until the sketches match without reference.
In terrestrial position fixing, the candidate plots a three-point fix, gets a cocked hat, and simply places the position at the centre of the triangle without checking for a systematic error or identifying which position line is suspect.
The cocked hat is treated as random scatter to be averaged. Candidates do not know that a constant offset in one bearing usually means a misidentified object or a compass/gyro error, and that a triangle whose sides are all similar suggests a random error while a triangle with one long side suggests one bad line.
What to do instead
Always bisect the cocked hat and, if it is large, re-identify each object, check the bearing book against the charted object, and test for a constant gyro error by comparing all three observed bearings with the bearings derived from a dead-reckoned position. If one line is clearly the outlier, discard it and fix on the remaining two. State the size of the cocked hat and the assumed position in the answer, never a bare coordinate.
When computing tidal height or an estimated time of high water from a standard port and a secondary port, the candidate applies the secondary-port differences with the wrong sign, or interpolates the tidal curve at the wrong reference (using the standard port's HW time instead of the secondary port's corrected time).
Secondary port corrections are given as differences and candidates rush the arithmetic, losing track of whether a difference is added or subtracted and of the order of operations (time correction first, then height correction, then the curve). The exam sets values that punish a sign slip.
What to do instead
Use a fixed written template: (1) standard port HW time and height, (2) apply secondary port time difference with explicit sign, (3) apply height differences to HW and LW separately, (4) compute the duration and the range at the secondary port, (5) enter the curve with the corrected times only. Show every line of the template in the answer so a sign error is visible, and do three worked examples per study session.
On passage planning questions, the candidate lists a track and waypoints but omits the safety checks: no abort/escape positions, no under-keel clearance calculation, no identification of no-go areas, traffic separation schemes, or contingency anchorages, and no statement of the chart and publication corrections used.
Candidates treat passage planning as drawing a line on a chart because that is the visible output, and they have not internalized that the exam is testing the appraisal and planning phases, not just the plot. They also forget that a plan must be executable if a diversion is needed.
What to do instead
Answer in the four-phase structure explicitly: appraisal (charts, publications, notices, weather, traffic, no-go areas), planning (track, waypoints with cross-track limits, wheel-over points, abort points, contingency anchorages, under-keel clearance with squat and allowance), execution, and monitoring. Name the specific publications and corrections checked. Write out at least two abort positions with the reason for each.
When asked for the action on detecting a developing tropical revolving storm or on interpreting a synoptic chart, the candidate gives the storm's bearing and distance but does not state the safe navigable semicircle, the recommended course to evade, or how the wind shift will reveal which side of the track the vessel is on.
Candidates memorize the definition of the dangerous and navigable semicircles but not the operational decision sequence: determine the bearing of the centre, the vessel's hemisphere, the direction of the storm's movement, then the evasion course. They also confuse the buy-ballot's-law wind shift with the actual observed veering/backing that tells them which side they are on.
What to do instead
Use a fixed sequence in every TRS answer: (1) fix the centre's bearing, (2) determine whether you are in the Northern or Southern Hemisphere, (3) determine the storm's track, (4) identify the semicircle, (5) give the evasion course for that hemisphere and semicircle, (6) state the wind shift that confirms your side. Practise with both hemispheres and both semicircles, and always state the reasoning, not just the course.
On ship stability numerical questions, the candidate substitutes values into a formula without checking units or the reference point, for example mixing tonnes and cubic metres in a KG or GM calculation, or using the wrong lever for a free-surface correction.
Stability formulas are learned as strings of symbols and candidates do not keep a mental model of what each quantity physically is. Under time pressure they skip the unit check and the free-surface correction, which is the step the exam most often tests.
What to do instead
For every stability calculation, write the formula, then write the units of each term before substituting, then compute. Always ask whether a free surface exists and apply the FSC (FSM/displacement) explicitly. Keep a one-page formula sheet with the physical meaning of each term and re-derive GM, KG, and list from first principles once per session. Check the answer's magnitude against a rough estimate.
On watchkeeping questions, the candidate describes the handover as a verbal report and omits the specific items that must be exchanged and the conditions under which the handover must be deferred, and treats the lookout requirement as satisfied by the OOW alone in clear weather.
Candidates learn watchkeeping as a list of duties rather than as a set of non-negotiable procedural checks. They do not recall that handover must include the vessel's position, course, speed, traffic, and status of machinery, and that the handover should be deferred if a manoeuvre or a situation requiring undivided attention is in progress.
What to do instead
Memorize a handover checklist and recite it: position and intended track, course and speed, traffic and risk of collision, machinery and steering mode, weather and visibility, navigational warnings, outstanding orders, and the state of the watch. State the deferral condition explicitly. For lookout questions, always distinguish the lookout's function from the OOW's and state that a proper lookout must be maintained by all available means including hearing and radar.
On radar and ECDIS questions, the candidate confuses what the equipment measures with what it derives: treating a radar ARPA track as a true-motion solution regardless of the display mode, or assuming an ECDIS safety contour and safety depth are the same setting.
Candidates learn buttons and menus without the underlying model of relative versus true motion, ground versus sea stabilization, and vector type. On ECDIS they conflate the safety contour (the depth at which the display alarms) with the safety depth (the value used for the four-colour shading) and with the shallow contour.
What to do instead
For radar, always state the display mode, the stabilization (sea or ground), and the vector type (relative or true) before interpreting any ARPA output, and explain how each changes the picture. For ECDIS, write out the four depth settings (shallow contour, safety contour, safety depth, deep contour) with their distinct functions and what each controls on the display. Practise interpreting a described radar picture from text only.
On emergency and pollution-prevention questions, the candidate answers with the general intent (for example 'inform the master and follow the SOPEP') without naming the specific signals, reports, or record entries, such as the GMDSS distress alert sequence, the MAYDAY/PAN PAN/SECURITE distinction, or the MARPOL Annex that applies to the spill described.
Candidates revise these topics as background reading and never drill the precise outputs the exam wants: the exact alert priority, the required report content, the annex and its discharge criteria, and the record book entry. They also blur distress, urgency and safety traffic.
What to do instead
Build a one-page card for each: GMDSS distress/urgency/safety alert sequence with the exact priority and acknowledgement path; the content of a distress message; the MARPOL annexes with the substance each covers and the discharge criteria; and the SOPEP immediate actions. For every emergency answer, state the alert, the report, the immediate action, and the record entry as four separate lines.
On cargo and dangerous goods questions, the candidate states the IMDG class number without the subsidiary risk, packing group, segregation requirement, or the stowage position relative to other cargo, and treats the class list as sufficient knowledge.
Candidates memorize the nine classes as a list and stop there, because the class names are the most visible part of the topic. The exam tests whether the candidate can act on the classification: segregation table, stowage on deck or under deck, and the documentation and marking required.
What to do instead
For each class, learn the subsidiary risks, the packing groups, the segregation rules against the other classes, the stowage category, and the required documents and markings. Practise with a described consignment: state the class, subsidiary risk, packing group, segregation from named other cargo, stowage position, and the documentation required. Always state the source publication used.
On seamanship and anchoring questions, the candidate gives the anchor cable scope as a single number without reference to depth, holding ground, or weather, and describes rigging or ropework in general terms without naming the knot, splice, or purchase and its specific use.
Candidates learn seamanship as vocabulary rather than as a decision procedure. They do not connect scope to depth and conditions, and they cannot name the specific knot or splice the situation requires, so they answer with a description that sounds plausible but is not operational.
What to do instead
For anchoring, always compute scope from the depth at the bow plus the freeboard, state the multiplier for the conditions (for example 5 to 7 times depth in good holding, more in poor holding or heavy weather), and state the veering and weighing procedure. For ropework and rigging, name the specific knot, splice or purchase and its use, and describe the failure mode it prevents. Drill with named situations rather than definitions.