Sterndrive Troubleshooting Quiz

Sterndrive Troubleshooting Quiz

by Conrad & Judy Kreuter

You have always taken pride in your ability to troubleshoot and diagnose stern drive engines and lower units. At the marina you are known as Dr. Sterndrive.

We are sure you know these Dr. Sterndrive types. Test your knowledge with this troubleshooting quiz to see how he rates versus what you know.

1) Your seven year old Alpha I generation II powered boat stalls when shifting from neutral into forward or reverse. The most likely cause is:
a) engine idle speed is too low
b) Seven years is old for a boat, it just doesn’t want to move anymore!
c) the shift cable is tight and must be replaced
d) the shift interrupt switch is not adjusted correctly

2) The shift interrupt switch on your Alpha I drive is not functioning. The most likely symptom is:
a) The drive will not go into forward gear
b) It takes excessive force to get the shift handle out of gear
c) You can’t start the boat
d) The drive makes a clunking noise when going into gear

3) You are taking a leisurely cruise around the lake and everything is fine. As you approach the dock the engine stalls and you can’t restart it. You can not hear the starter motor engaging when turning the key. What could be wrong?
a) The alternator went bad and the battery is not being recharged.
b) A battery lead fell off during the cruise
c) You have not shifted into neutral before attempting to restart the engine
d) You ran out of gas

4) Your Alpha I drive goes into gear okay at the dock and as long as the rpm isn’t over 2500 everything seems fine. When accelerating to bring the boat up on plane, you notice a random clunking noise which causes the boat to shutter. What could be wrong?
a) You have both a worn clutch dog and forward gear
b) The shift cable is misadjusted
c) You think you hit bottom
d) The noise is coming from the cooler as the beer cans fall over upon acceleration

5) After cruising for some time at normal speed, suddenly the engine rpm goes up and the boat slows down. A strong burning rubber smell is evident. What happened?
a) The rubber hub on the propeller failed
b) An alternator belt is loose
c) The engine coupler failed
d) The drive trimmed itself up due to a malfunction of the trim pump

6) When you depress the trim button on the control handle in the up direction everything works fine. Depressing the down button won’t make the drive go down. The most common cause is:
a) The down circuit fluid needs to be changed
b) The down relay is defective
c) The switch in the handle is defective
d) A crab is caught in the drive not letting it go down

7) You have noticed that over the last few boating seasons the temperature gauge has been reading a few degrees higher each season. What’s going on here?
a) Global warming has increased the water temperature
b) Maybe it’s time to change the water pump
c) Cooling water flow is being restricted by clogged manifolds and risers
d) This is normal, engines work harder when they get older, hence higher temperatures

8) During the winter layup season, you tuned the engine installing new plugs, points, rotor, condenser, and distributor cap. The engine ran fine before winter layup. In the spring, the engine turns over but will not start. Why?
a) You have installed the rotor backwards
b) You forgot to install the rotor
c) The points have been in the open position all winter and have oxidized
d) The plugs are fouled with fogging oil

9) Your motor turns over but will not start. It is getting fuel. You have troubleshot the ignition system and have found a no spark condition. Which components could be faulty?
a) Spark plugs
b) Ignition coil
c) Tachometer
d) Both b and c

10) You have a convential ignition system (points, rotor, condenser, etc) and every few hours of operation the ignition coil stops working. This has happened at least twice before. What can you do to fix this problem?
a) Buy a high quality racing ignition coil
b) Change the spark plug wire set
c) Add a series resistor to the 12v lead of the coil
d) Install a new high energy solid state ignition system

11) This is your first year with a new Alpha drive. You have removed the 6 mounting nuts and power trim cylinders from the outdrive but the outdrive will not come off the boat. What’s wrong?
a) The outdrive is glued on at the factory, use a bigger pry bar
b) The shift lever must be in forward gear to remove the drive
c) The shift lever must be in reverse gear to remove the drive
d) Salt has corroded the drive to the gimbal housing

12) You have taken your know-it-all mechanic out for a spin. He mumbled something about a bearing toward the rear of the boat that is growling. He said it should be changed. Which bearing is he talking about?
a) muffler bearing
b) self lubricating bearing and hoffer shaft
c) gimbal bearing
d) top drive shaft bearing

13) You are attempting to remove an Alpha I outdrive for routine maintenance. The shifter is in forward gear and you have removed all six mounting nuts and the power trim cylinder assemblies yet you cannot remove the drive from the boat. Why?
a) The engine alignment changed causing the drive shaft spline to bind within the engine coupler.
b) A hole in the universal bellows boot has allowed seawater to enter. Salt-water corrosion has caused the binding of the driveshaft within the gimbal bearing.
c) A large pry bar and heavy hammer are always necessary to remove the drive.
d) Barnacles have positioned themselves over the drive-to-gimbal housing joint making it impossible to remove the drive.

14) You have just completed a major tune-up on your 5.7-liter V-8 engine with HEI ignition. The engine is very hard to start, or if does start, runs for a short time, backfires and dies. You have checked the timing, made sure the ignition wires are connected to the correct spark plug, and the compression is okay. What happened?
a) The rotor wheel is installed upside down.
b) The fuel pump relay is defective.
c) The rotor that was installed is from a V-6 motor
d) The distributor cap is defective

15) Your V-6 4.3L engine stalls when shifting from neutral to forward or reverse. Upon removing the drive, salt-water corrosion is evident within the shift shaft area. The shift shaft boot appears intact with no leaks. The problem is:
a) a worn seal on the shift shaft
b) a defective gasket between the outdrive and transom assembly
c) a defective o-ring on the shift cable
d) cracked housing on the lower unit

16) Your V-8 powered I/O has no power. Timing and compression are within specs. Recently the motor overheated due to a run in with a sand bar, however you are sure all the related problems were fixed. Any ideas?
a) Due to the overheat some or all of the valves are tuliped
b) The overheat caused the manifold to crack letting water into some of the cylinders
c) The overheat melted the exhaust flappers which have dislodged from their mounting, fallen into the exhaust Y pipe, and are blocking the exhaust.
d) The overheat condition caused the ignition advance curve in the ignition module to change.

17) In the spring the boat received a much needed compounding and wax job. Upon launching the boat you find the engine will start and stall some time later. You suspect a fuel problem. When you open the gas tank filler cap, the sound of rushing air can be heard. What could be wrong?
a) The fuel pump is bad
b) The fuel filter has an air leak
c) Debris from the compound and buffer wheel clogged the fuel tank vent
d) The air filter is dirty and must be replaced

18) You have been fishing all day with your young son. At one time, fishing line was entangled with the lower unit. While driving home the alarm sounds. Upon checking the possible causes for the alarm signal, you discover a low gear oil condition in the lower unit monitor. What should you do?
a) Add gear oil to the lube monitor
b) Pull the propeller and inspect for fishing line
c) Have the lower unit checked for pressure and vacuum, repair as needed
d) All of the above

19) A good friend asked you to look over a boat he is considering purchasing. The boat has been in storage a few years. Everything looks ok except for one freeze out plug that is missing. What would your recommendation be?
a) Buy the boat, a freeze out plug is easy to replace
b) The boat was most likely stored improperly and there may be other internal engine damage
c) All hoses and belts should be changed
d) None of the above

20) Last year you winterized your 4.3-L engine and boat on the trailer. Upon start up this year, water is seen coming from a crack in the exhaust elbow. You are positive enough antifreeze was added to the engine. Why did this happen?
a) Depending upon fore and aft angle of the engine, fresh water could get trapped within the manifolds, which when allowed to freeze, may crack the manifold
b) You did not add enough antifreeze
c) You used antifreeze with the incorrect burst protection
d) A small leak is ok

21) Your 3.0L engine with conventional ignition starts but does not run well above 1500 RPM and lacks power. A complete tune-up did not solve the problem. What could be wrong?
a) The ignition timing module is defective
b) Initial timing is incorrect
c) Mechanical weights within the distributor are frozen which will not allow timing to advance
d) Engine is under sized for the boat

22) Your V-8’s compression is the same on all cylinders except one. Why?
a) You dropped the compression gauge during the test
b) Most likely a valve is not closing all the way
c) Compression ring on the spark plug is defective
d) Excessive carbon on piston or valve will cause higher than normal compression reading.

23) The boat has just been launched for the first spring ride. You bring up the throttle to the red line and the engine bucks and misses at top RPM. The engine runs smooth at all RPM’s otherwise. Why?
a) Cracked anode on the spark plug
b) Defective ignition wires
c) The overrev limiter is activating
d) Defective ignition module

24) After a day’s outing, a routine check of your oil reveals a level higher than normal. Why?
a) Leaking head gasket is allowing fuel to drain into oil pan
b) The oil generator switch is defective
c) Incorrect dip stick has been used to check the oil level
d) The oil filter bypass circuit is activated due to a clogged oil filter

25) Your wife surprised you by thoroughly cleaning the boat. Unfortunately, she left the engine cover off while she was spraying down the boat. Now the boat won’t start. Why?
a) She got water in the carburetor
b) The engine cover ripped off a few spark plug wires
c) Water in the distributor cap is shorting out the ignition
d) The battery got wet and shorted the terminals


1) c
2) b
3) c
4) a
5) c
6) b
7) c
8) c
9) d
10) b
11) b
12) c
13) b
14) c
15) a
16) c
17) c
18) d
19) b
20) a
21) c
22) b
23) c
24) a
25) c

  • 25 Wow, you can work on my motor anytime!
  • 22-24 Consider yourself an ace marine mechanic
  • 15-21 Fairly respectable troubleshooting skills
  • 8-14 Better brush up on your I/O knowledge before leaving shore
  • 0-7 Don’t let them see you coming at the marina