Troubleshooting Quiz

OB Troubleshooting Quiz

by Conrad & Judy Kreuter

Last month, we ran a trouble-shooting quiz to see how much you really know about stern drives. This month the outboard wizards get to belly up to the bar and test their troubleshooting knowledge with the following questions. Let’s see how you do.

1) A 1994 V-4 Evinrude spits and stalls at idle. The thermostats have been replaced, and all the carburetors have been rebuilt and adjusted twice. Engine cylinder head temperature reads 128 degrees. There is still no resolution to this problem. What else could be wrong?
A) A spit at idle is a lean condition that could be caused by a crankcase leak
B) Replace all the carburetors with new
C) Rejet the offending carburetor to richen up the mixture
D) Add additional oil to the gas mixture

2) Your boat has a full complement of gauges including a tachometer. Upon start up, the tachometer zeroes out but will not record the proper RPM. What could cause this problem?
A) +12V power lead going to the tach has come loose
B) Tachometer gauge is bad
C) Rectifier/Regulator is bad
D) All of the above

3) Your 70HP 3 cylinder Johnson spits at idle. A measurement of the cylinder head temperature indicates 80 degrees with water temperature of 55 degrees. The most likely cause is:
A) 80 degree cylinder head temperature is normal for this water temperature
B) A lower heat range spark plug has been installed, change to the proper heat range
C) The thermostat is stuck open or has been removed
D) The thermostat is stuck in the closed position

4) A friend has a V-6 engine that needs repair. It is hard to start and runs rough at all speeds. You have taken out the spark plugs and a few of them are salt water fouled indicating water within the cylinders. Which is the most logical sequence of repairs?
A) Change the cylinder head gasket, exhaust plate gasket, and then the powerhead base gasket
B) Change the exhaust plate gasket, powerhead base gasket
C) Change the cylinder head gasket, check the cylinder head for distortion, exhaust plate and then the powerhead base gaskets
D) Condemn the engine, it has a cracked block

5) Your friend has been troubleshooting his motor for a few days. The compression is equal and the spark is good on all cylinders. The engine is getting plenty of fuel. The battery is turning over the engine at the correct RPM. Yet, the engine will not start. What could be wrong?
A) The engine safety lanyard is not attached
B) The choke solenoid is defective
C) The flywheel key is sheared
D) The black/yellow wire to the CDI box is shorted to ground

6) Each time the ignition switch is turned to the start position, the main wire harness fuse blows. The main wire harness has been checked and is okay. Why is the fuse blowing?
A) The fuse is undersized, install a larger fuse
B) The starter solenoid coil winding is shorted
C) Starter motor is partially shorted and is drawing excessive current
D) The fuse holder terminal ends are corroded

7) An Evinrude175HP V-6 only reaches 5,000 RPM. The factory spec is 5,600. Changing the prop to a lower pitch has no effect on top end RPM. Compression is okay and all cylinders have good spark. Where should you look now?
A) Check the spark plugs, one or more may be fouled
B) Check the fuel supply, it may be restricted.
C) Check maximum spark advance adjustment
D) Check the boat for an overweight condition

8) After 3 fishing trips, the battery in your trailered boat goes dead. Why?
A) The battery will not hold a charge
B) The rectifier/regulator is defective
C) There is a small leak in the boat causing the bilge pump to work more than normal
D) The battery terminal ends need to be cleaned

9) A1989 88HP SPL Johnson starts fine and runs good when cold. After warm up, applying throttle causes the engine to stall. The fuel supply system is in good condition. What is the most likely cause?
A) Carburetor float is set to high
B) The VRO low oil level switch is defective
C) The fuel primer bulb is defective
D) The fuel pump diaphragm is weak

10) Your 1994 175HP Mercury has given you many years of dependable service. The boat always came up on plane at 3,200 RPM. Lately however, you must be at 4,000 RPM to get on plane. Compression, ignition and fuel are okay. Why?
A) Someone changed the prop with out you knowing it
B) You have started fishing with “Big Billy”
C) The tachometer is giving you the wrong reading
D) You used to boat in a lake, now you are in salt water which is heavier

11) When you leave the boat at the marina you always tilt the motor to the up position, but never put on the tilt lock lever. After a week the motor is in the down position. What would you do to solve this problem?
A) Use the tilt lock lever

B) Change the tilt switch mounted on the motor
C) Drain and refill the trim/tilt resoviour, metal particles are stuck in the up lock valve
D) Bring it to the dealer and let him solve the problem

12) A 225HP Johnson is hard to shift. The control box, shift cables and lower unit are within factory specifications. What else could be wrong?
A) Weak upper and lower motor mounts are allowing the lower unit to bind on the shift shaft
B) The shift interrupt switch is defective
C) The idle is set to high
D) Lubricate the shift cable

13) A V-6 engine starts okay and performs well for the first 3 minutes of medium speed operation. At that time the engine speed drops 400 RPM. This trouble will happen every time the motor is used. Why?
A) The gas filter is clogged
B) A stator winding is failing when warm
C) A CDI unit is failing when warm
D) An ignition coil is failing when warm

14) A V-6 engine runs poorly at medium to high speeds. Removing the air baffle reveals fuel being spit out of one of the carburetors. Why?
A) A reed valve is bent or broken
B) The piston must be bad because it is not producing enough vacuum
C) The carburetor base gasket is leaking
D) The fuel pump is supplying too much fuel

15) An OMC V-6 with an optical ignition system sounds the overheat warning buzzer. Temperature checks at the cylinder head indicate normal operation. What could be wrong?
A) Dirt and debris are clogging one cylinder head
B) One or both temperature switches are defective
C) The warning buzzer circuit in the control box is defective
D) The tan wire in the main wiring harness is shorted

16) You have just completed changing the water pump. Upon testing the engine on the boat, the steering pulls to one side. What have you done to cause this problem?
A) Nothing, changing the water pump could not effect steering
B) Torque tab was not installed correctly
C) Torque tab was not tightened down
D) Torque tab was not installed

17) After changing the water pump on a V-6 Johnson, the unit does not shift correctly and clunks when going into gear. Why?
A) The shift rod and shift linkage are not connected
B) Change to a heavy weight gear oil to eliminate the noise
C) The shift rod was loose so you tightened it
D) The new water pump impeller is putting an additional strain on the gear case

18) A 225HP Mariner with EFI has an ignition problem. At idle, the timing fluctuates about 2 degrees. What could be wrong?
A) Crank Position sensor is not properly set
B) Loose or poor ground connections
C) Defective engine temperature sensor
D) It is normal for timing to change on this model

19) A 200HP Yamaha surges upon acceleration. What would be the best way to test for the cause of this condition?
A) Connect a pressure gauge between fuel pump and carburetors
B) Connect a vacuum gauge between the fuel filter and motor
C) Operate the motor with a known good gas tank
D) Replace the fuel filter

20) A 225HP EFI Mercury is hard to start when cold. Why?
A) The ECU is not advancing the timing for cold start
B) Defective temperature switch
C) Defective enrichment valve
D) All of the above

21) A motor with a PTT system runs but the trim system does not move up or down. Which one of the following would not cause this problem?
A) Low oil level
B) Pump assembly faulty
C) Manual release valve leaking or not fully closed
D) Tilt ram piston leaking

22) When rebuilding a gearcase, which of the following operations should be performed?
A) All bearings should be cleaned and inspected
B) All defective bearings and races should be changed as a set
C) All seals should be changed regardless of condition
D) All of the above

23) A gearcase was extremely hard to remove. The problem was a rusted drive shaft spline. The rusted spline was cleaned and greased. The gearcase will not seat properly during installation. Why?
A) Grease is trapped in the clearance area between the driveshaft spline and crankshaft
B) The crankshaft still has rust on it
C) Because it was so hard to remove, the drive shaft elongated
D) The driveshaft is not entering the crankshaft, rotate the driveshaft and reinstall

24) Which of the following are not normally found on an EFI 4-stroke motor?
A) Intake air control valve
B) Intake air temperature sender
C) Manifold absolute pressure sensor
D) Oxygen sensor

25) In a four stroke engine, what part of the camshaft operation is very similar to the loop scavenge method of a 2-stroke engine?
A) Cam lobe duration
B) Cam lift
C) Overlap
D) Opening and closing ramp design

1) A- Never rejet a carburetor unless it is for use at higher altitudes
2) C
3) C- A open or missing thermostat causes low cylinder head temperature therefore the engine cannot operate at the proper temperature
4) C
5) C- A sheared flywheel key will allow spark, but it will not occur at the proper time
6) B- The main harness fuse is used to make sure defective components do not overload and burn the wire harness
7) B
8) B
9) D
10) C
11) C- Often the only repair is to replace the complete pump assembly
12) A
13) D
14) A
15) B
16) B- Tech Tip- before removing the torque tab, mark its location with a felt tip marker. Align the mark during installation.
17) C
18) D
19) C- By eliminating the fuel supply as a cause of this problem it can be determined if the engine is at fault or the fuel supply
20) D- All the listed parts assist in starting a cold engine
21) D
22) D
23) A
24) D- Typically the oxygen sensor is only used during testing
25) C

20-25 Either you’re an expert or were peeking at the answers
15-19 Very decent troubleshooting skills
8-14 Keep reading that shop manual
0-7 Let professionals work on your engine