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Power & Propulsion Exam and Solutions


Have you been paying attention to advice given in this column?

All right gearheads, listen up! I appreciate that you’re regular readers of this column, but have you really absorbed useful information from it? Let’s see just how good your retention level is. Here are 10 questions on topics I’ve covered here over the past 12 months or so. If you are a careful reader you should have no problem answering them. For those of you who need a little help or just want some verification of your acumen, the answers are at the bottom. But be honest—NO PEEKING! Here we go:

1. In a properly installed automatic engine-room fire-suppression system (pick all that are correct):
  a. The bottle and outlet should be on the centerline, at about mid-height so you can easily access them
  b. The bottle can be anywhere but the outlet(s) should be down low where they will be more effective putting out oil and fuel fires
  c. The bottle can be anywhere but the outlet(s) should be as high up as possible and ideally over the top of the engines
  d. The bottle and discharge nozzle can be anywhere as long as the bottle’s vertical to make sure all the extinguishing agent gets expelled

2. Which one of the following statements is not true?
  a. Conventional wet-cell batteries require ventilation and should be in waterproof battery boxes to prevent damage from leakage
  b. Gel Cells and AGMs are both types of Valve-Regulated Lead-Acid (VRLA) batteries
  c. Because they don’t off-gas, VRLA batteries don’t require ventilation
  d. Because their electrolyte is retained in glass mats, AGM batteries will not leak if their case is breached

3. Cutless bearings are called that because (choose one):
  a. The front of them is sharp and curved, like a cutlass
  b. The name is actually the trademark of a company that designed rubber bearings
  c. They’re named after the Oldsmobile Cutlass, which pioneered this type of bearing design
  d. The bearing housing is shaped so that it’s less likely to cut the rubber bearing as it wears

4. Most experts agree that to find an optimum balance between speed and wear the best rpm to cruise gas engines is (choose one):
  a. Two-hundred rpm off of the rpm at which the engine is rated
  b. The slower, the better
  c. The rpm that engines make the least noise and vibration
  d. Between 3400 and 3800 rpm

5. When doing an engine survey prior to buying a boat, which one of the following is not a good idea?
  a. Conduct a sea trial instead of doing an oil analysis
  b. Make sure the owner or owner’s rep is present
  c. Have the mechanic onboard while the boat is underway
  d. Ask to see all maintenance records

6.  Answer True or False to the following statements:
  a. The majority of engine wear takes place at startup
  b. It’s okay to let a diesel engine idle for long periods of time because it burns so little fuel
  c. Always let your engine idle for a few minutes to warm up before getting underway
  d. Oil temperature is the best indicator of when an engine is up to operating temperature

7.  Which of the following should you not be wearing when you enter a live engine room?
(choose all that apply.)

  a. Ear protection
  b. Loose-fitting clothing
  c. Glasses
  d. Jewelry

8. Spectrographic analysis is a valuable diagnostic tool for evaluating (choose one):
  a. Engine lube oil
  b. Engine coolant 
  c. Marine-gear oil
  d. All of the above

9. If your engines are turning at their rated rpm according to your tachometers (choose all that apply):
  a. They must be making their full horsepower
  b. Your props are necessarily correct
  c. Your boat could still be underpropped and your engines may not be making full horsepower
  d. Your boat could be overpropped

10. Diesel fuel is (pick one):
  a. More susceptible to contamination by water than gasoline because it tends to stay in storage tanks longer
  b. More susceptible to contamination by water than gasoline because it is less volatile
  c. Less susceptible to contamination by water than gasoline because water settles to the bottom of the tank where it’s not a problem
  d. About as susceptible to water contamination as gasoline

Power & Propulsion Solutions

Caterpillar  C8.7

Caterpillar’s New C8.7

Answers to Exam:
 1. C
 2. C
 3. B
 4. D
 5. A
 6. True; False; False; True
 7. B and D
 8. D
 9. C
 10. B

At the 2014 Fort Lauderdale International Boat Show, Caterpillar officially unveiled its new C8.7, which it had announced earlier in the year. This 8.7-liter, in-line, six-cylinder engine is unusual in that it utilizes both a turbocharger and a mechanically-driven radial supercharger. The idea behind this unusual pairing is that the supercharger provides instant boost until there is sufficient exhaust gas volume to allow the turbocharger to take over, after which it automatically disengages. The result is said to be elimination of turbo lag and much quicker planing. Rated at 650 metric horsepower at 2300 rpm, this Tier 3-compliant engine also features common-rail fuel injection, left and right service options, and a standard electric fuel-priming pump. Beside applications in conventional inboards, the C8.7 is also designed to pair up with the CAT Three60 Pod 650 pod-drive system (shown above), which will be available in the fall.

ZF Hybrid-Ready Transmissions

If you’ve been thinking of doing a build or refit with the goal of creating a “greener” yacht and are considering a hybrid (diesel and electric) drive system, you’ll be happy to know that ZF has a line of marine gears that have been engineered specifically to accommodate alternative power inputs to the propeller via a Power Take-In (PTI) on the marine gear itself. For low-speed operation such as docking or station-keeping, these gears will allow you to take the main engines offline and maneuver using more efficient power sources such as electric and hydrostatic motors and small diesel engines. Because the PTI can be ordered with a wide variety of gear ratios and spur gears (for reverse rotation), nearly any size auxiliary motor can be utilized. ZF’s hybrid-ready transmissions are available with capacities ranging from around 2,000 horsepower to more than 13,000 horsepower.

This article originally appeared in the February 2015 issue of Power & Motoryacht magazine.