For diesel engines, such as those used for main propulsion and auxiliary power on river push boats, while running at speed, how is the ignition of fuel within the cylinder achieved?

Ignition is achieved by the heat of compression created by compressing intake/charge air within the cylinder into a relatively small volume.

Ignition is achieved by the heat of compression created by compressing the air/fuel mixture within the cylinder into a relatively small volume.

Ignition is achieved by intense heat by passing electric current through the element of a specially designed glow plug.

Ignition is achieved by a high voltage electric spark induced across the gap of a specially designed spark plug.

Ignition is achieved by the heat of compression created by compressing intake/charge air within the cylinder into a relatively small volume.

You are assigned to a fishing industry factory ship fitted with main propulsion diesel engines of the type shown in the illustration. If the engine's crankshaft is turning at 900 rpm, what will be the rotational speed of the two camshafts?

Not enough information is given to determine camshaft rpm

You are assigned to a fishery research vessel fitted with main propulsion diesel engines operating on the cycle represented in the polar timing diagram shown in the illustration. When do the intake valves open and close respectively?

The intake valves open at 75° before top dead center on the exhaust stroke. The intake valves close at 45° after bottom dead center on the compression stroke.

The intake valves open at bottom dead center at the end of the intake stroke. The intake valves close at top dead center at the beginning of the intake stroke.

The intake valves open at 45° after bottom dead center on the compression stroke. The intake valves close at 75° before top dead center on the exhaust.

The intake valves open at top dead center at the beginning of the intake stroke. The intake valves close at bottom dead center at the end of the intake stroke.

The intake valves open at 75° before top dead center on the exhaust stroke. The intake valves close at 45° after bottom dead center on the compression stroke.

The uninspected fishing trawler to which you are assigned is fitted with main propulsion diesel engines of the type shown in the illustration. In terms of valve operating gear, cylinder liner type, and connecting rod type, what statement is true?

This is a pushrod operated overhead valve engine, with wet cylinder liners and conventional connecting rods

This is an overhead cam engine, with jacketed cylinder liners and marine-type connecting rods

This is an overhead cam engine, with wet cylinder liners and conventional connecting rods

This is a pushrod operated overhead valve engine, with wet cylinder liners and conventional connecting rods

This is a pushrod operated overhead valve engine, with jacketed cylinder liners and articulated connecting rods

When checking the crankcase oil level on a main propulsion engine on your fishing industry line vessel while underway, what should be the oil level as indicated on the dipstick?

The level should be between the "full" and "add" marks on the side of the dipstick marked with engine IDLE and oil HOT.

The actual level is unimportant as long as it is visible on the dipstick when the engine is running.

The level should be between the "full" and "add" marks on the side of the dipstick marked with engine IDLE and oil HOT.

The level should be below the "add" mark on the side of the dipstick marked with engine IDLE and oil HOT.

The level should be well above the "full" mark on the side of the dipstick marked with engine IDLE and oil HOT.

After an emergency shoring installation has been completed, the __________.

shoring should be frequently inspected for looseness

repair is completed and no further action is needed

timbers are nailed in place to prevent looseness

damaged plating should be straightened by heating

An acceptable method of temporarily sealing a crack formed in the hull of a vessel is to __________.

apply a patch of sheet packing backed by a strongback or shoring

tack weld a doubler plate over the crack

shore up the crack with welded braces

Which of the following conditions represents a particular advantage of using a positive pressure type self- contained breathing apparatus in an atmosphere that is immediately dangerous to life or health?

The positive pressure in the facepiece prevents contaminated air from entering the facepiece.

The equipment is compact and the wearer can work in confined spaces without difficulty.

The average operating time for most air cylinders is over an hour.

The positive pressure in the facepiece prevents contaminated air from entering the facepiece.

The equipment used is lightweight and easy to wear by reducing physical strain on the wearer.

Which of the devices listed would be safe to use in a compartment with insufficient oxygen?

Self-contained breathing apparatus.

What is meant by the term emergency bilge suction?

The means by which the machinery space bilge is pumped out by a pump not normally used as a bilge pump and drawing a suction directly on the bilge independent of any bilge manifolds or automatic bilge suction valves.

The means by which the machinery space bilge is pumped out by a pump not normally used as a bilge pump and drawing a suction on the bilge through either bilge manifolds or automatic bilge suction valves.

The means by which the machinery space bilge is pumped out by a pump not normally used as a bilge pump and drawing a suction directly on the bilge independent of any bilge manifolds or automatic bilge suction valves.

The means by which the machinery space bilge is pumped out by a pump normally used as a bilge pump and drawing a suction directly on the bilge independent of any bilge manifolds or automatic bilge suction valves.

The means by which the machinery space bilge is pumped out by a pump normally used as a bilge pump and drawing a suction on the bilge through either bilge manifolds or automatic bilge suction valves.

If an air compressor is fitted with a hand-off-auto (H-O-A) control station, what statement concerning operation is true?

In the hand mode, the compressor will run continuously with unloading.

In the hand mode, the compressor will cycle on and off.

In the auto mode, the compressor will run continuously with unloading.

In the off mode, the compressor will cycle on and off.

Which of the following liquid level sensors would be most suitable for measuring the liquid level in a pressure vessel, such as a water-tube boiler steam drum?

Displacement float level sensor

With respect to shaft bearing load absorption capability in terms of direction, what is meant by an axial load?

An axial load is a load applied parallel to the axis of the shaft.

An axial load is a load applied tangent to the circumference of the shaft.

An axial load is a load applied perpendicular and parallel to the axis of the shaft.

An axial load is a load applied perpendicular to the axis of the shaft.

UFIV – Assistant Engineer Practice Test

What is on the UFIV – Assistant Engineer exam

Module	Questions	Illustrations	Practice
Q690 Motor Plants	50	25	Practice →
Q692 Engineering Safety & Environmental Protection	50	3	Practice →
Q693 General Subjects	50	12	Practice →
Total	150	40

Most modules require 70 percent to pass; Rules of the Road modules require 90 percent.

Q690 · 50 questions · 25 illustrations

Motor Plants

All Motor Plants and Auxiliary Boilers questions Sit Q690 timed

1. For diesel engines, such as those used for main propulsion and auxiliary power on river push boats, while running at speed, how is the ignition of fuel within t...
2. You are assigned to a fishing industry factory ship fitted with main propulsion diesel engines of the type shown in the illustration. If the engine's crankshaft...
3. You are assigned to a fishery research vessel fitted with main propulsion diesel engines operating on the cycle represented in the polar timing diagram shown in...
4. The uninspected fishing trawler to which you are assigned is fitted with main propulsion diesel engines of the type shown in the illustration. In terms of valve...
5. When checking the crankcase oil level on a main propulsion engine on your fishing industry line vessel while underway, what should be the oil level as indicated...

Showing the first 5 of 50. Start at question 1 and use Next to work through the module →

Q692 · 50 questions · 3 illustrations

Engineering Safety & Environmental Protection

All Engineering Safety questions Sit Q692 timed

Showing the first 5 of 50. Start at question 1 and use Next to work through the module →

Q693 · 50 questions · 12 illustrations

General Subjects

All General Subjects questions Sit Q693 timed

Showing the first 5 of 50. Start at question 1 and use Next to work through the module →

UFIV – Assistant Engineer exam FAQ

Q How many questions are on the UFIV – Assistant Engineer exam?

The National Maritime Center's 2026 sample examination for UFIV – Assistant Engineer has 150 questions across 3 modules: Q690 Motor Plants (50 questions), Q692 Engineering Safety & Environmental Protection (50 questions) and Q693 General Subjects (50 questions). Every one is multiple choice with four answers, and you can practice all of them on this page.

Q What modules are on the UFIV – Assistant Engineer exam?

The modules are Q690 Motor Plants (50 questions), Q692 Engineering Safety & Environmental Protection (50 questions) and Q693 General Subjects (50 questions). Each module is graded separately, so you need to pass every one to pass the exam.

Q What score do I need to pass the UFIV – Assistant Engineer exam?

Most USCG exam modules require 70 percent to pass; Rules of the Road modules, where they apply, require 90 percent. Check the specific requirements for your endorsement with the National Maritime Center.

Q Are these the real questions?

Yes. They are the questions on the National Maritime Center's published 2026 sample examination for UFIV – Assistant Engineer (modules Q690–Q693), matched to our bank of released U.S. Coast Guard exam questions. The exam you sit draws from the same pools.

Q Can I take a timed UFIV – Assistant Engineer practice exam?

Yes. Subscribers can sit any module as an official sample exam in its published order, timed or untimed, with answers revealed at the end. Free accounts can build one 10-question practice exam and answer questions on every module page.

Other engine practice tests

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UFIV – Assistant Engineer Practice Test

What is on the UFIV – Assistant Engineer exam

Motor Plants

Engineering Safety & Environmental Protection

General Subjects

UFIV – Assistant Engineer exam FAQ

Q How many questions are on the UFIV – Assistant Engineer exam?

Q What modules are on the UFIV – Assistant Engineer exam?

Q What score do I need to pass the UFIV – Assistant Engineer exam?

Q Are these the real questions?

Q Can I take a timed UFIV – Assistant Engineer practice exam?

Other engine practice tests

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