6 HP 8 HP 9.9 HP 10 HP 15 HP 20 HP 25 HP Mercury Mariner Outboard 2 Stroke CDI Switch Box 855713A4
PRODUCT DETAILS
CDI Unit / Power Pack / Switch Box for Mercury & Mariner Outboards
High-quality marine-grade aftermarket CDI ignition unit / power pack / switch box for selected Mercury and Mariner 6 HP, 8 HP, 9.9 HP, 10 HP, 15 HP, 20 HP and 25 HP 2-stroke outboard engines.
Designed for selected:
2 Cylinder – 2 Stroke – 4 Magnet Flywheel
Mercury / Mariner outboards manufactured approximately 1997–2006, depending on the exact horsepower, model and serial number.
Designed as a replacement for:
855713A3 / 855713A4
Fits Selected Mercury / Mariner Outboards
6 HP
Selected:
- 2 Stroke
- 2 Cylinder
- 4 Magnet Flywheel
- Approx. 1997–2005
8 HP
Selected:
- 2 Stroke
- 2 Cylinder
- 4 Magnet Flywheel
- Approx. 1997–2005
9.9 HP
Selected:
- 2 Stroke
- 2 Cylinder
- 4 Magnet Flywheel
- Approx. 1997–2005
10 HP
Selected:
- 2 Stroke
- 2 Cylinder
- 4 Magnet Flywheel
- Approx. 1997–2005
Including selected:
- 10 HP
- Sea Pro
- Marathon
applications depending on serial number and specification.
15 HP
Selected:
- 2 Stroke
- 2 Cylinder
- 4 Magnet Flywheel
- Approx. 1997–2006
Including selected standard and commercial applications depending on serial number.
20 HP
Selected:
- 2 Stroke
- 2 Cylinder
- 4 Magnet Flywheel
- Approx. 1998–2006
Including selected standard and commercial applications.
25 HP
Selected:
- 2 Stroke
- 2 Cylinder
- 4 Magnet Flywheel
- Approx. 1998–2006
Including selected:
- 25 HP
- 25 XD
- Sea Pro / Marathon applications
depending on exact engine specification.
Fitment Summary
| HP | Engine | Cylinders | Approx. Application |
|---|---|---|---|
| 6 HP | 2 Stroke | 2 | 1997–2005 |
| 8 HP | 2 Stroke | 2 | 1997–2005 |
| 9.9 HP | 2 Stroke | 2 | 1997–2005 |
| 10 HP | 2 Stroke | 2 | 1997–2005 |
| 15 HP | 2 Stroke | 2 | 1997–2006 |
| 20 HP | 2 Stroke | 2 | 1998–2006 |
| 25 HP | 2 Stroke | 2 | 1998–2006 |
Selected applications use a:
4 MAGNET FLYWHEEL
⚠️ IMPORTANT
The year ranges are a guide only.
Do NOT assume every Mercury / Mariner 6–25 HP engine manufactured during these years uses this CDI.
Replaces Mercury / Mariner Part Numbers
- 855713A3
- 855713A4
Also searchable as:
- 855713-A3
- 855713-A4
- 855713 A3
- 855713 A4
- 855713
Additional Cross References
- CDI Electronics 114-5713
- CDI 1145713
- Sierra 18-99222
OEM manufacturer names and part numbers are provided for identification and compatibility reference only.
⚠️ VERY IMPORTANT – 4 MAGNET FLYWHEEL
This CDI / switch box is designed for selected 1997–2006 Mercury / Mariner 2-cylinder 2-stroke engines using a 4-magnet flywheel ignition system.
Please check your engine before ordering.
Do not select the CDI simply because your engine is:
- 6 HP
- 8 HP
- 9.9 HP
- 10 HP
- 15 HP
- 20 HP
- 25 HP
Mercury / Mariner used different ignition systems across these horsepower ranges.
⚠️ IMPORTANT – Check Your Existing CDI
Before ordering, compare your existing CDI / switch box carefully.
Check:
- Original part number
- Electrical plugs / connections
- Wiring configuration
- Number of cylinders
- Flywheel / ignition system
- Complete engine serial number
- Mounting arrangement
Ideally, your original switch box should cross-reference to:
855713A3 or 855713A4
Different From Earlier 339-7452A CDI
Mercury / Mariner used a different CDI / switch-box family on many earlier 6–25 HP 2-cylinder engines.
Earlier Engines – Approx. 1980–1997
Common switch-box family:
339-7452A19 / 339-7452A15
Later Engines – Approx. 1997–2006
This listing:
855713A3 / 855713A4
These CDI units are NOT interchangeable simply because the horsepower is the same.
Always identify the ignition system and original part number before ordering.
What Is a CDI / Switch Box?
The CDI / switch box is an important component of the Mercury / Mariner ignition system.
It receives electrical signals from the ignition system and controls the electrical output used to fire the ignition coils.
A faulty CDI / switch box can be associated with symptoms such as:
- No spark
- Intermittent spark
- Loss of spark on one cylinder
- Difficult starting
- Misfiring
- Engine cutting out
- Loss of ignition when hot
- Irregular engine operation
Important
These symptoms do not automatically mean the CDI is faulty.
Similar problems can be caused by the stator, trigger, ignition coils, stop circuit, wiring or poor electrical connections.
Proper diagnosis is recommended before replacing the CDI.
Product Features
- Marine-grade aftermarket CDI unit
- CDI ignition module
- Power pack
- Switch box
- Suitable for selected Mercury outboards
- Suitable for selected Mariner outboards
- 6 HP
- 8 HP
- 9.9 HP
- 10 HP
- 15 HP
- 20 HP
- 25 HP
- 2 Stroke
- 2 Cylinder / Twin Cylinder
- Selected 4-magnet flywheel applications
- Approx. 1997–2006
- Replacement for 855713A3
- Replacement for 855713A4
- Cross-reference CDI 114-5713
- Direct replacement for compatible applications
- New aftermarket ignition component
⚠️ Appearance Does Not Confirm Fitment
If the CDI looks the same as the one fitted to your engine, this does not always mean it is the correct part for your outboard.
Different Mercury / Mariner CDI units can look very similar but have different:
- Internal specifications
- Wire connections
- Ignition-system requirements
- Applications
Please check the original part number and complete engine details before purchasing.
Before Replacing Your CDI / Switch Box
If your engine has an ignition fault, we recommend checking the complete ignition system before installing a replacement CDI.
Check:
- Stator output
- Trigger output
- Ignition coils
- Spark plugs
- Spark plug leads
- Stop / kill circuit
- Engine earth / ground connections
- CDI wiring
- Electrical plugs and connectors
- Burnt or corroded terminals
- Damaged or melted wiring
A fault elsewhere in the ignition system can produce symptoms similar to a failed CDI and may damage a replacement component.
Aftermarket Replacement Part
This is a high-quality marine-grade aftermarket replacement part.
It is not a genuine Mercury, Mariner or Quicksilver component.
OEM manufacturer names and part numbers are provided for identification and compatibility reference only.
The component is designed as a replacement for compatible Mercury / Mariner applications using:
855713A3 / 855713A4
What's Included
1 × CDI Unit / Power Pack / Switch Box
New aftermarket replacement component.
Buyer Responsibility
It is the buyer's responsibility to confirm compatibility before purchasing.
Please check:
- Engine horsepower
- 2-stroke engine
- 2-cylinder configuration
- Complete engine serial number
- Original CDI part number
- Electrical connections
- 4-magnet flywheel application where applicable
If you are unsure, please send SSI Marine:
Engine horsepower + complete serial number + clear picture of your existing CDI and connections
Our technical team will be happy to help identify the correct ignition unit.
Why Buy From SSI Marine?
- Marine-grade aftermarket & OEM-spec parts
- Workshop-tested products
- More than 10 years supplying and working with outboard engines
- Same-day dispatch before 1 PM Monday–Friday
- Royal Mail Tracked 24
- UK stock
- Collection available from Leigh, Greater Manchester
- Technical support from experienced outboard specialists
- Workshop open Monday–Friday, 9 AM–5 PM
SHIPPING & DELIVERY
Delivery & Returns Policy
Delivery
Standard Delivery
- £6: Royal Mail Tracked 24 Service
- £3.99: Large Letter - Royal Mail 1st Class Post (Untracked)
We offer free delivery on all orders over £150 (excludes outboard engines).
Orders placed before 1:00 PM (Monday-Friday) are usually dispatched the same working day.
Most parcels are delivered within 24 hours, but please allow extra time for courier delays that may occur outside our control.
For outboard engines, please contact us for a delivery quote.
Important: Please ensure your shipping address is correct before completing checkout. SSI Marine is not responsible for parcels sent to an incorrect address provided by the buyer.
Tracking Your Order
Once your order has been dispatched, you will receive a tracking number via email (after 5 PM on the day of dispatch).
Tracking is available only for parcels sent via Royal Mail Tracked 24.
Large Letter orders are sent via Royal Mail 1st Class Post (untracked).
Returns
We accept returns of unused and undamaged items within 30 days of purchase.
Returned items must be in sellable condition and include the original packaging.
Please do not tape, label, or write directly on the product's original box.
Important: Do not return items in their original product boxes only, they must be placed inside a protective outer box or bag. Parcels returned like the example below will be subject to a 20% restocking fee.
Return shipping costs are the customer's responsibility.
Please include your order details and reason for return inside the parcel.
Refunds
Refunds are issued for the item purchase price only (shipping costs are non-refundable).
All refunds will be made using the same payment method as your original order.
Items returned in poor condition or without proper packaging may incur a 20% restocking fee.
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