The Seiko 8M25A is a specialized digital quartz movement created for professional sailing and yacht race timing. It offers a precise countdown timer function tailored to pre-race start sequences, along with a stopwatch, alarm, and standard digital timekeeping. The 8M25A was part of Seiko’s advanced marine sports range in the early 2000s and continues to be appreciated for its utility, durability, and compact layout in regatta-focused watches.
Caliber Number: 8M25A
Movement Type: Quartz (Digital LCD)
Primary Functions:
Time display (12-hour or 24-hour format)
Yacht countdown timer (up to 10 minutes)
Automatic switch to stopwatch after countdown
Chronograph (stopwatch mode up to 99 minutes, 59 seconds)
Daily alarm
Audible beep signals (minutely and last 10 seconds)
Battery Type: CR2025 lithium coin cell
Battery Life: Approximately 5 years
Accuracy: ±20 seconds per month
Water Resistance: Varies by case, often 100–200 meters
Display Type: Multi-field Liquid Crystal Display (LCD)
Typical Button Count: 4 external pushers
Digital display shows hours, minutes, and seconds
Optional AM/PM (12-hour) or 24-hour display
May include day-of-week and date fields depending on model
Accuracy is maintained at ±20 sec/month under normal temperature ranges
Designed for yacht racing pre-start
Countdown range: 1 to 10 minutes, selectable in 1-minute increments
Audible alerts:
Single beep at every elapsed minute
Beep every second for the final 10 seconds
After countdown reaches zero, the movement automatically switches to chronograph mode to measure race time
Activated either manually or automatically after countdown
Measures up to 99 minutes, 59 seconds
Displays elapsed time with split-second precision
Useful for timing race segments or total duration
Daily alarm function
Set by hour and minute
Audible tone signals at the preset time
Can be toggled on/off manually
Watches equipped with the Seiko 8M25A movement typically have four pushers:
A (Top Left) – MODE: Cycles through TIME → COUNTDOWN → CHRONOGRAPH → ALARM
B (Bottom Left) – SET: Enters setting mode, clears or resets values
C (Top Right) – START/STOP: Begins or halts timing functions
D (Bottom Right) – ADJUST: Changes timer values, toggles alarm, switches 12/24-hour formats
Enter Time Mode using Button A
Hold Button B until the hour field flashes
Use Button D to adjust
Press Button B to switch to minutes
Press Button A to confirm and exit
Enter Countdown Mode with Button A
Hold Button B until countdown digits flash
Use Button D to select desired countdown length (1–10 minutes)
Press C to start countdown
Press C again to pause
Press B to reset
Enter Alarm Mode
Hold Button B until hour field flashes
Use Button D to set hour, then press B to switch to minutes
Toggle alarm ON/OFF with Button D in alarm mode
Confirm with Button A
CR2025 lithium 3V coin cell
Lifespan: ~5 years under normal usage
Remove the old battery
Insert new CR2025 (positive side up)
Locate the AC terminal on the circuit board
Use metal tweezers to short the AC contact to the battery’s negative terminal
Hold for 2–3 seconds
Display resets and all segments briefly illuminate
Reprogram time, countdown, and alarm as needed
Without this reset, the screen may stay blank or show incorrect data.
Fully electronic – no lubrication required
Clean contact springs and buttons during battery service
Replace case gaskets to maintain water resistance
Avoid exposure to magnetic fields and high-impact conditions
Rinse with fresh water after saltwater use and dry thoroughly
The 8M25A was installed in Seiko Prospex Yacht Timer models and certain marine chronograph designs, including:
Seiko Prospex Regatta Timer
Models with reference numbers like SBBNXXX, SBBJXXX, and other Japan Domestic Market (JDM) exclusives
Notable for:
Large, legible LCD screens
Button guards and rugged bezels
Integrated resin or polyurethane straps
100–200 m water resistance
Feature | Detail |
---|---|
Countdown Range | 1 to 10 minutes |
Stopwatch | Up to 99 min 59 sec |
Alarm | Daily, programmable |
Display Format | LCD, 12/24-hour |
Battery Type | CR2025 |
Battery Life | Approx. 5 years |
Reset Required | Yes – AC after battery change |
The Seiko 8M25A is a professional digital yacht timer movement, engineered with competitive sailing in mind. Its ability to count down to race starts with audible cues, then seamlessly switch to stopwatch mode, provides a serious edge to regatta crews and race officials. Easy to operate, robust in construction, and efficient in performance, it represents a practical and reliable tool for marine sports applications. Today, it remains a favorite among Seiko tool-watch enthusiasts and sailing professionals.
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