Mercury 8.1S Horizon, Product Applications Manual

Page: 57 / 163

Air Intake System
Page 4A-4 90-863758060 AUGUST 2006
5. Route the manometer hose to allow reading the engine compartment differential
pressure.
6. Position another thermocouple above the flame arrestor on the engine to read the peak
engine compartment temperatures.
7. Be sure the hoses, thermocouples, and fittings stay away from moving parts. Use a tie
strap if necessary.
8. Zero the pressure gauge before starting the engine.
9. Start the engine and check for fuel leaks.
Running Test
1. Record the ambient air and water temperature.
2. Operate the boat at WOT for 10 minutes.
3. Operate the boat at 1000, 2000, 3000, 4000 RPM, and WOT and record fuel inlet
temperature and pressure.
4. Record maximum engine compartment pressure differential at WOT.
5. Bring the boat to idle (in or out of gear) and continue to idle for 15 minutes.
IMPORTANT: Do not operate generators, blowers or any other type of equipment that can
displace air from the engine compartment.
IMPORTANT: Do not open the engine compartment during the test.
6. At the end of 15 minutes, record the engine compartment air temperature, fuel
temperature and fuel pressure.
7. Rapidly accelerate to WOT and maintain WOT for about 30 seconds. Ensure that there
is plenty of room and no danger to other boaters.
8. Do not close the throttle if a hesitation, stumble, bog or stall occurs. Allow the engine
to recover (if possible) on its own.
9. Observe operating characteristics and record the highest fuel pressure drop seen
during WOT run.
10. Complete heat soak test and then refer to Interpreting Results .
Heat Soak Test
1. Operate the boat at WOT for 10 minutes.
2. Bring the boat to an idle, anchor and shut off engine.
3. Record the fuel temperature and engine compartment air temperatures at 5 minute
intervals until the highest temperature has been observed. This may take up to 2½
hours. If the temperature has remained the same for 10–15 minutes or begins to lower,
the maximum has probably been reached.
IMPORTANT: Do not operate generators, blowers or any other type of equipment that can
displace air from the engine compartment.
IMPORTANT: Do not open the engine compartment during the test.
4. Once the temperature has stabilized, start the engine and idle for 10 seconds. This
should give time to turn the boat or clear obstacles. Rapidly accelerate to WOT and
maintain WOT for about 30 seconds. Ensure that there is plenty of room and no danger
to other boaters.
5. Do not close the throttle if a hesitation, stumble, bog, or stall occurs. Allow the engine
to recover (if possible) on its own.
6. Observe operating characteristics and record the highest fuel pressure drop seen
during the WOT run.