USCG Deck General Exam Study Guide: Every Topic Covered

The Deck General module is the broadest written exam in the USCG license exam suite. At the Master 100 GT and 200 GT level it runs 100 questions; even at the OUPV level, deck general content makes up the largest single category. It covers seamanship, stability, cargo operations, anchoring, weather, towing, and more — the practical knowledge of running a commercial vessel.

This study guide covers every major topic category, what depth the exam expects, and the references that align closest to what the NMC question bank actually draws from.

Stability

Stability is conceptually the hardest topic in Deck General. The exam tests it at two levels: qualitative (understanding what makes a vessel more or less stable) and quantitative (calculating the effect of loading changes).

Key Terms and Concepts

G (Center of Gravity): The point through which all of the vessel's weight acts downward. Lower G = more stable vessel. Raises when you add weight above G; lowers when you add weight below G.

B (Center of Buoyancy): The geometric center of the displaced water volume. Moves as the vessel heels.

M (Metacenter): The point about which the vessel appears to rotate when heeled at small angles. When M is above G (positive GM), the vessel has initial stability and will right herself.

GM (Metacentric Height = KM - KG):

• Positive GM = vessel is stable — she'll return to upright after a small heel
• Negative GM = vessel is unstable — she'll roll over to a new equilibrium
• Very high GM = "stiff" vessel — snappy rolling motion, uncomfortable but not dangerous
• Very low GM = "tender" vessel — slow, sluggish rolling, but vulnerable to large waves

GZ (Righting Arm): At angles beyond initial stability, GZ is the horizontal distance between G and B, which generates the righting moment. The GZ curve (static stability curve) shows how righting arm changes with heel angle.

KG calculations: When you load or discharge weight, KG changes:

New KG = (Ship's displacement × old KG) ± (weight added/removed × its height above keel) / new displacement

Adding weight above the current G raises G. Adding weight below the current G lowers G.

Free surface effect: Liquid in partially filled tanks creates a free surface. As the vessel heels, the liquid shifts to the low side, effectively raising G and reducing GM. The correction: GG₁ = (free surface moment) / (vessel displacement), where free surface moment = (length × breadth³/12) × density ratio of the liquid.

What the Exam Tests

• Calculate new KG after loading/discharging weight
• Determine whether loading a weight raises or lowers GM
• Identify which action will increase GM (pump out a high tank, lower weights, add ballast to double-bottom tanks)
• Explain free surface effect and how to minimize it (keep tanks either full or empty when possible)
• Interpret a stability letter — what maximum allowable KG means for a given loading

References

Barras' Ship Stability for Masters and Mates is the best reference for USCG exam-level stability content. Chapman Piloting Chapter on trim and stability is a lighter introduction.

Anchoring

Scope Calculation

Scope = ratio of cable paid out to depth of water (from hawse pipe to bottom).

The classic formula: Cable length = scope × depth

The exam commonly asks: vessel anchors in 30 feet of water with scope of 7:1. How much cable does she pay out? Answer: 7 × 30 = 210 feet. Add the height of the hawse pipe above the water surface for accuracy.

Adequate scope for normal conditions: 5:1. Heavy weather or strong current: 7:1 to 10:1.

Anchor Types

• Stockless anchor (Navy pattern): Most common on commercial vessels; easy to stow in the hawse pipe; good holding power in most bottoms
• Danforth anchor: High holding power to weight ratio; good in sand and mud; limited in rock
• CQR (Plow anchor): Plows into soft bottom; resets after direction change; common on pleasure craft
• Kedge (Standard stock anchor): Traditional "fisherman" anchor; good in rocky bottom; difficult to stow

The exam asks about which anchor is appropriate for different bottom types and conditions.

Dragging Anchor

Signs of a dragging anchor: bearing to a charted object changes; GPS track shows movement opposite wind/current; chain becomes taught and vibrates. Response: check scope, pay out more chain, back down gently to set better, or re-anchor in a better position.

Weather Interpretation

Frontal Systems

Cold front: Fast-moving, steep frontal slope. Weather sequence: warm southerly winds → rapidly backing wind, rapid barometric fall, sharp temperature drop, heavy rain, gusty winds. After passage: cold northwest wind, clearing, rising barometer. Small craft advisory typical ahead of fast-moving cold fronts.

Warm front: Slower-moving, gentle frontal slope. Weather sequence: high cirrus clouds → lowering overcast → prolonged rain (sometimes hours before the front reaches you) → warm/moist southerly air after passage. Limited wind shift at passage.

Occluded front: Cold front overtaking warm front. Combined characteristics. Prolonged cloud cover and precipitation.

Tropical Cyclones

The "1-2-3 Rule" (Dangerous Semicircle): In the Northern Hemisphere, a tropical cyclone rotates counterclockwise. The right front quadrant (dangerous semicircle) has the strongest winds because the storm's forward speed adds to the cyclonic wind speed. The navigable semicircle (left half) has weaker winds.

Maneuvering to avoid: On the right (dangerous) side: back your wind on the starboard bow, make as much headway as possible. On the left (navigable) side: bring the wind on the starboard quarter and run.

Beaufort Wind Scale: The exam occasionally tests Beaufort numbers. Know that Force 7 (28-33 knots) = near gale; Force 8 (34-40 knots) = gale; Force 10 (48-55 knots) = storm. Small craft advisories are typically issued at Force 6 (22-27 knots).

Lines and Rigging

Deck Lines and Their Uses

Mooring lines: Bow line (forward), stern line (aft), spring lines (prevent fore-and-aft motion). After bow spring runs aft from the bow; forward quarter spring runs forward from the stern quarter.

Block and tackle terminology: A purchase system. The mechanical advantage depends on the number of parts of line supporting the load. A luff tackle (double block at load, single at hauling part) has a mechanical advantage of approximately 3:1.

Line Strength

Natural fiber: manila, sisal. Synthetic: nylon (best for dock lines — stretches to absorb shock), polypropylene (floats, good for tow pennants), polyester (Dacron — low stretch, used where dimensional stability matters), high-modulus polyethylene (HMPE/Dyneema — extremely strong, low stretch, expensive).

Safe working load vs. breaking strength: The exam uses a safety factor typically of 5:1 or 6:1. SWL = Breaking Strength / Safety Factor.

Towing

Small Vessel Towing Concepts

Catenary: The natural sag in a tow line. More catenary = more shock-absorbing capacity. In heavy weather, a longer tow line with good catenary is preferable to a short, taught wire. Nylon lines have inherent catenary due to stretch.

Tow length: In open water, a long tow reduces snatch loads. In restricted waters, a shorter tow gives better control. In waves, match tow length to a multiple of the wave length so both vessels ride up waves together.

Emergency towing: If power fails, the towing vessel should attempt to come alongside and re-rig. A bridle attached to two strong points distributes the load. Always have a quick-release or cutting tool accessible to the tow line.

Stability Under Fire Conditions

Not commonly addressed in fire training but tested in stability: fighting a vessel fire with large volumes of water can create significant free surface in the bilge and on the weather deck. The high weight of accumulated water can reduce stability to critical levels. Know when to stop firefighting water application and consider pumping or scuttling to control stability.

Sample Study Schedule for Deck General

Week 1: Stability concepts — work through KG calculations daily, understand GM and the effect of loading changes.

Week 2: Anchoring, mooring, and rigging. Memorize scope rules, anchor types, and block-and-tackle mechanical advantage.

Week 3: Fire classification and extinguishing, PFDs, distress signals.

Week 4: Weather — frontal systems, tropical cyclone avoidance, Beaufort scale.

Week 5-6: Practice full Deck General sessions, drilling any category that's scoring below 75%.

Chapman Piloting, Seamanship and Small Boat Handling is the best single reference for USCG Deck General content at the OUPV and 100-ton level. It covers stability, weather, seamanship, and fire in well-organized, exam-appropriate depth.

Practice with Binnacle School

Deck General is the most diverse exam module — it tests everything from GM calculations to tow line catenary. [Binnacle School](/school) gives you category-specific practice within Deck General so you can identify whether you're weak on stability, weather, or seamanship specifically — and drill each independently rather than grinding through mixed question banks.

Start your Deck General exam prep at Binnacle School →

Binnacle AI is not affiliated with the U.S. Coast Guard or the NMC. Exam content reflects current NMC guidance as of 2026 — verify at uscg.mil/nmc. Not legal advice.