The Seiko 8M37A is a digital quartz movement purpose-built for sailing and regatta timing. As one of the final evolutions in Seiko’s 8M-series yacht timers, it combines key marine sports features: a programmable countdown timer, automatic transition to chronograph, daily alarm, and audible signal cues—all presented on a durable, marine-optimized digital LCD platform. The 8M37A was used in some of Seiko's most advanced regatta timers under the Prospex and Marine Master labels in the mid-2000s.

Technical Specifications

• Caliber Number: 8M37A

• Movement Type: Quartz (Digital LCD)

• Display Format: Multi-segment Liquid Crystal Display

• Functions:

  • Timekeeping (12-hour or 24-hour format)

  • Countdown timer (adjustable: 1 to 10 minutes)

  • Auto-switch to stopwatch (chronograph) at 0

  • Stopwatch (up to 99 minutes 59 seconds)

  • Daily alarm

  • Audible buzzer with race countdown indicators

  • Optional hourly time signal

• Battery Type: CR2025 (3V lithium coin cell)

• Battery Life: Approx. 5 years

• Accuracy: ±20 seconds per month

• Reset Type: AC (All Clear) reset required after battery replacement

• Backlight: Electroluminescent (model-dependent)

• Water Resistance: Case-dependent (typically 100–200 meters)

Functional Overview

1. Timekeeping Mode

• Standard digital time display

• 12-hour or 24-hour selectable format

• Seconds, minutes, and hours displayed continuously

• AM/PM indicator shown in 12-hour mode

• Primary display in normal mode

2. Regatta Countdown Timer

• Designed for pre-race starts

• Settable from 1 to 10 minutes in 1-minute increments

• Audible indicators:

  • One beep per elapsed minute

  • Beep every second during final 10 seconds

• At 0:00, the timer automatically starts the chronograph to track race duration

• Prevents user error during race transitions

3. Stopwatch (Chronograph) Mode

• Measures elapsed time up to 99 minutes, 59 seconds

• Can be started manually or triggered via countdown timer

• Stopwatch can continue in the background while viewing other modes

• Start/Stop and Reset functions via dedicated buttons

4. Daily Alarm Mode

• Alarm set by hour and minute

• Loud piezo buzzer

• Can be toggled ON/OFF via dedicated button input

• Functions independently of timer or stopwatch

Button Functions

Watches using the 8M37A typically feature four buttons in a symmetrical layout:

• A (Top Left): MODE — Cycles through TIME → TIMER → CHRONO → ALARM

• B (Bottom Left): SET — Activates setting mode or resets functions

• C (Top Right): START/STOP — Controls countdown and stopwatch

• D (Bottom Right): ADJUST — Adjusts values, toggles alarm

The buttons are built for use in wet environments and often include anti-slip grooves or guards.

Setting Instructions

A. Set the Time

1. Press A to enter Timekeeping mode

2. Hold B until hours flash

3. Use D to adjust

4. Press B to move to minutes and toggle 12H/24H format

5. Press A to confirm and exit

B. Set the Countdown Timer

1. Press A to enter Timer mode

2. Hold B until the minute field flashes

3. Use D to select countdown length (1–10 minutes)

4. Press C to start

5. Press C again to pause

6. Press B to reset to original value

C. Use the Stopwatch

1. Press A to enter Chronograph mode

2. Press C to start and stop

3. Press B to reset to zero

D. Set the Alarm

1. Press A to enter Alarm mode

2. Hold B until the hour flashes

3. Use D to adjust hour

4. Press B again to adjust minutes

5. Toggle alarm ON/OFF with a short press of D

6. Confirm and return by pressing A

Battery Replacement & AC Reset

Battery:

• CR2025, 3V lithium coin cell

• Replace every ~5 years under normal usage

AC Reset Procedure:

1. Install the new battery

2. Locate the AC terminal (marked on PCB)

3. Use metal tweezers to short the AC terminal to the battery’s negative side (case or spring contact)

4. Hold for 2–3 seconds

5. LCD will flash and reset

6. Re-set time, countdown, and alarm after reset

Failure to perform the AC reset may result in an unresponsive display.

Maintenance Notes

• Movement is fully electronic — no lubrication required

• Replace gaskets and pressure test during battery changes

• Rinse in fresh water after saltwater exposure

• Avoid magnetism and strong impacts

• Backlight and beeper functionality may weaken as the battery nears end-of-life

Watch Models Featuring the 8M37A

The Seiko 8M37A was featured in Seiko Prospex Yacht Timer and Marine Timer watches. Common design elements include:

• Large digital LCD screen with electroluminescent backlight

• Water resistance rated from 100 m to 200 m

• Reinforced stainless steel or resin cases

• Rugged, oversize buttons

• Strap options in rubber, polyurethane, or stainless steel

Examples include SBEF003, SBEF009, and other Japan Domestic Market (JDM) models.

Summary Table

Conclusion

The Seiko 8M37A is a precise, durable, and function-focused digital yacht timer movement, developed specifically for regatta racing and sailing events. Its seamless countdown-to-chronograph transition, clear digital display, and rugged case integration make it a reliable tool for competitive skippers. As one of Seiko’s final evolutions in its marine quartz timer series, the 8M37A offers maximum performance with minimal fuss—ideal for professionals and collectors alike.