Garmin GPSMAP 451 Installation Manual

The Garmin GPSMAP 451 is a high-performance marine chartplotter featuring a 4-inch diagonal color display, built-in worldwide basemap, preloaded BlueChart g2 coastal charts, support for NMEA 0183 and NMEA 2000 networks, waterproof design (IPX7), and sunlight-readable screen. This manual covers essential information for safe and proper installation, configuration, and initial setup of your GPSMAP 451 unit on your vessel.

1. Package Contents 2. Mounting Considerations 3. Power Connection 4. NMEA Network Connection 5. Antenna & Sensor Connections 6. Initial Power-On & Setup 7. Configuration Settings 8. Safety Information 9. Specifications 10. Troubleshooting

Package Contents

Before beginning installation, verify you have all components.

Item	Description
GPSMAP 451 Unit	Main chartplotter display
Mounting Bracket & Hardware	For flush or bracket mounting
Power/Data Cable	Includes fuse holder and connectors
Documentation	Quick start manual, safety sheet
Protective Cover	For storage or transport

Note: Some bundles may include a Garmin G2 Vision or BlueChart g2 data card. Check your specific package.

Mounting Considerations

Select a location that ensures safe operation and clear visibility.

Viewing Angle: Mount within arm's reach and at a comfortable viewing angle to minimize glare.
Accessibility: Ensure access to the SD card slot, power button, and connector port.
Clearance: Allow space behind the unit for cable connections and ventilation.
Surface: Mount on a flat, sturdy surface using the provided template.
Water Drainage: If flush mounting, ensure the cutout allows for any potential water drainage.

WARNING! Do not mount where it will obstruct the operator's view of the helm or waterways. The mounting surface must be strong enough to support the unit's weight and vibration.

Power Connection

Connect the unit directly to the vessel's battery for best performance.

Identify the red (power) and black (ground) wires on the power/data cable.
Connect the red wire to the positive (+) terminal of the battery or a switched 12 VDC power source through the provided in-line fuse (3 A).
Connect the black wire to the negative (-) terminal or vessel ground.
Secure all connections with crimp connectors and protect with heat-shrink tubing or electrical tape.
Route the cable away from high-current wires and sources of interference.

CAUTION! Always install the fuse on the positive lead as close to the power source as possible. Ensure the power is OFF during installation.

NMEA Network Connection

The GPSMAP 451 can interface with other marine electronics for data sharing.

NMEA 0183: Use the blue (TX/A), brown (RX/A), green (TX/B), and yellow (RX/B) wires to connect to compatible devices (e.g., VHF radio, autopilot). Refer to your other device's manual for wiring details.
NMEA 2000: To connect to a NMEA 2000 network, you will need a Garmin NMEA 2000 starter kit or compatible cable to connect the unit's port to the backbone.

Tip: Proper NMEA 0183 connections require matching transmit (TX) wires to receive (RX) wires on the other device, and sharing a common ground.

Antenna & Sensor Connections

The unit has a built-in GPS antenna. For enhanced data, connect external sensors.

Connection	Purpose	Wire/Cable
External GPS Antenna	Improved satellite reception (optional)	Garmin GA 29 or compatible
Temperature Sensor	Water temperature data	Garmin TMP or NMEA 2000
Depth/Speed Transducer	Depth, water speed, temperature	Compatible Garmin transducer

Follow the specific sensor's installation manual for mounting and wiring instructions. Ensure all underwater fittings are properly sealed.

Initial Power-On & Setup

After connections are secure, power on the unit.

Turn on the vessel's power or switch on the 12 VDC source.
Press and hold the POWER button on the front of the GPSMAP 451.
The unit will perform a self-test and display the Garmin splash screen.
Follow the on-screen prompts to:
- Set language and units (metric/nautical).
- Agree to the terms and conditions.
- Configure initial map and display settings.
The unit will begin searching for GPS satellites. For first lock, ensure you have a clear view of the sky; this may take several minutes.

Configuration Settings

Access the main menu to configure your system.

Key Setup Pages:

System: Set backlight, sounds, units, time format, and system information.
Navigation: Configure navigation alarms, map orientation (North Up/ Course Up), and route preferences.
Communications: Set up NMEA 0183 sentences (enable/disable) and configure NMEA 2000 device list if connected.
Sensors: Calibrate or configure connected speed, temperature, or depth sensors.
Charts: Manage chart cards, select chart detail levels, and set safety shading.

Use the ROCKER key to navigate menus and press ENTER to select.

Safety Information

This device is a navigation aid only and must not be used for precise navigation.

Always compare GPS-derived positions with known landmarks and other navigation methods.
Do not mount the unit where installation or maintenance will distract the operator.
Ensure all wiring does not pose a tripping hazard or interfere with vessel operation.
The unit is waterproof (IPX7) but connectors are not. Ensure the cable connector is fully seated and the cap is secured when not in use.

WARNING! The operator is solely responsible for the safe navigation of the vessel.

Specifications

Display: 4" diagonal, 480 x 272 pixels, color TFT, sunlight readable.
Waterproof Rating: IPX7 (submersible in 1 meter of water for 30 minutes).
Power Input: 10–35 VDC, 3 A max (fused).
Internal GPS: High-sensitivity receiver.
Data Storage: Accepts preprogrammed Garmin data cards (microSD/SD).
Interfaces: NMEA 0183, NMEA 2000, external antenna input.
Operating Temperature: -15°C to 55°C (5°F to 131°F).
Dimensions (W x H x D): Approx. 14.2 x 10.2 x 5.8 cm (5.6" x 4.0" x 2.3").

Troubleshooting

Symptom	Possible Cause	Corrective Action
Unit will not power on	No power, blown fuse, loose connection	Check battery voltage; inspect and replace fuse (3 A); verify power and ground connections are secure.
No GPS signal	Poor sky view, first-time acquisition	Move to an open area; wait up to 5–10 minutes for initial lock. Ensure no metal obstructions overhead.
Incorrect depth/speed data	Sensor not connected, fouled transducer	Check sensor wiring in System > Sensors menu. Clean transducer face of debris or growth.
No communication with NMEA devices	Incorrect wiring, wrong NMEA sentences enabled	Verify NMEA 0183 wiring connections. Enable required sentences in Communications > NMEA 0183 Setup.
Chart card not recognized	Card not fully inserted, corrupted card	Power off, remove and reinsert card firmly. Try a different, known-good chart card.

Reset: If the unit becomes unresponsive, press and hold the POWER button for 10 seconds to force a power cycle. For a factory reset, go to System > Reset.

Support: For further assistance, visit support.garmin.com or contact Garmin Product Support.