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Why Boats Use Knots Instead of Kilometers or Miles per Hour

  • Writer: VELOMOTORS VELOCÍMETROS
    VELOMOTORS VELOCÍMETROS
  • 1 minute ago
  • 3 min read

When people think about speed, they usually imagine kilometers per hour (km/h) or miles per hour (mph) — common units for cars and highways.However, in the marine world, speed is measured in knots, a system that may seem unusual at first, but makes perfect sense for navigation at sea.


Understanding why boats use knots helps boat owners better interpret GPS data, marine displays, MFDs, and instrument panels, especially when diagnosing speed-related issues.


What Is a Knot?


A knot is a unit of speed equal to one nautical mile per hour.

To put it simply:

  • 1 knot = 1.15 mph

  • 1 knot = 1.85 km/h

This unit is internationally standardized and used in:

  • Marine navigation

  • Aviation

  • Nautical GPS systems

  • Chart plotters and multifunction displays (MFDs)


The Historical Origin of Knots

The term knot dates back to the 17th century, long before GPS or electronic instruments existed.

Sailors measured speed using a device called a chip log, which consisted of:

  • A wooden board thrown into the water

  • A rope with evenly spaced knots

  • A timing method, usually a sandglass

As the ship moved forward, the rope unspooled. Sailors counted how many knots passed during a fixed time interval.That count directly represented the vessel’s speed — and the name “knots” remained in use ever since.


Why Nautical Miles Are Used at Sea


Unlike land travel, marine navigation relies on latitude and longitude, not road distance.

A nautical mile is based on the Earth’s geometry:


  • 1 nautical mile = one minute of latitude

  • This simplifies distance calculation on nautical charts

  • It accounts for Earth’s curvature

Because of this, nautical miles — and therefore knots — integrate perfectly with:

  • Marine charts

  • GPS positioning

  • Autopilot systems

  • Radar and navigation instruments

This is why the same system is used worldwide, including in aviation.


Knots in Modern Marine Electronics


Today, knots are still the standard unit displayed on:

  • Marine GPS units

  • Multifunction displays (Raymarine, Garmin, Simrad, Lowrance)

  • Jet ski instrument clusters

  • Engine monitoring systems

Speed data is usually calculated by:

  • GPS signal

  • Paddle wheel sensors

  • CAN or NMEA 2000 network data

When a display shows incorrect speed readings, the issue is often related to:

  • Sensor failure

  • GPS module problems

  • Corrupted data on the CAN/NMEA network

  • LCD or backlight degradation affecting visibility


Common Speed Display Problems We See in the Shop


At Velomotors Technology, we frequently service marine displays with issues such as:

  • Dark or unreadable LCD screens

  • Speed values missing or frozen

  • Incorrect knot readings

  • Backlight failure after sun exposure

  • Water intrusion affecting GPS or sensor circuits

These problems can mislead operators and compromise navigation safety.


Why Understanding Knots Matters for Boat Owners


Knowing how knots work helps you:

  • Interpret your GPS and speed data correctly

  • Detect abnormal readings early

  • Communicate more effectively with marine technicians

  • Avoid unnecessary part replacements

In marine electronics, accurate data presentation is just as important as the data itself.


Professional Marine Electronics Repair You Can Trust


At Velomotors Technology, we specialize in:

  • Marine GPS and MFD repair

  • Instrument cluster restoration

  • LCD and backlight replacement

  • CAN and NMEA 2000 diagnostics

  • Jet ski and boat electronic systems


📦 We accept mail-in repairs and offer fast turnaround times.

👉 If your marine display shows incorrect speed, dark screens, or intermittent readings, contact us today and let our experts restore your equipment to full performance.

 
 
 
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