SECTION THREE — Installing the 491
Choosing a mounting location
Before any drilling or cutting takes place, carefully choose a mounting location for the 491 module that meets the following criteria:
•where the transducer cable is kept securely away from other wires
•where the path for running the required electrical cabling is reason- ably direct; keep in mind the different cable lengths
•where the 491 won’t be exposed to water
•where the status indicator (on the front of the 491) can be observed for system testing and troubleshooting.
NEVER MOUNT THE 491 MODULE IN THE BILGE!
Mounting the 491
Figure 7 shows the mounting dimensions for the 491. The 491 may be mounted either horizontally or vertically.
The mounting template supplied with the unit may be helpful in plan- ning the installation and locating the mounting holes. The keyhole slots make installation in hard-to-reach areas easier, but be sure to tighten all mounting screws securely. Leave room for installing and removing cables.
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| 8.78 |
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0.190 dia. |
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| 2.90 |
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| 2.90 |
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0.360 dia.
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| 491 Echo Sounder |
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| BNT Marine Electronics |
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| 30 Sudbury Road |
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| Acton MA 01720 |
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| www.NorthstarNav.com |
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| #1 Speed Sig |
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| +V |
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| #2 Speed | |||
| 8 Watts |
| #4Thermistor |
| #3 Speed | Gnd |
Allow space |
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| #5 Depth Lo + | #7Thermistor | ||
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| #8 Depth Hi + | #6 Depth Lo – | |||
for cabling from |
| STATUS | #10 Depth Hi – | #9 Depth Shields | ||
POWER |
| DATA | TRANSDUCER | |||
connectors.
2.35 
6.24 7.22
0.190 dia.
Dimensions in inches
0.75
FIGURE 7: 491 mounting dimensions and connector locations
PAGE 14 | 491 INSTALLATION MANUAL Revision A |