CDI Unit / Power Pack / Switch Box for Mercury & Mariner Outboards

Marine-grade aftermarket CDI ignition unit (power pack / switch box) replacing 855713A3 / 855713A4 on selected Mercury and Mariner 6, 8, 9.9, 10, 15, 20 and 25 HP 2-stroke, 2-cylinder outboards with a 4-magnet flywheel, approx. 1997–2006.

Fitment (approximate guide only)

6, 8, 9.9, 10 HP: approx. 1997–2005 (includes selected Sea Pro / Marathon)
15 HP: approx. 1997–2006
20 and 25 HP: approx. 1998–2006 (includes selected 25 XD, Sea Pro / Marathon)

All applications are 2-stroke, 2-cylinder with a 4-magnet flywheel. Mercury / Mariner used several ignition systems across these horsepowers, so horsepower and year alone do not confirm fitment, and a similar-looking unit is not always the right one.

Part numbers & cross references

Replaces: 855713A3, 855713A4 (also listed as 855713-A3, 855713-A4, 855713)
Cross reference: CDI Electronics 114-5713 / 1145713, Sierra 18-99222
Not the earlier 339-7452A15 / A19 family used on approx. 1980–1997 engines. These are not interchangeable.

Before you order

Check your original CDI part number, plugs and wiring, cylinder count, flywheel type and full engine serial number. Faulty stator, trigger, coils, stop circuit or wiring can mimic CDI failure, so diagnose the full ignition system first. Unsure? Send SSI Marine your engine horsepower, complete serial number and a clear photo of your existing CDI and connections, and our technical team will identify the correct unit.

What's included

1 × new aftermarket CDI unit / power pack / switch box. This is a high-quality marine-grade aftermarket part, not a genuine Mercury, Mariner or Quicksilver component. OEM names and part numbers are for identification and compatibility reference only. Confirming compatibility before purchase is the buyer's responsibility.

Why buy from SSI Marine

UK stock, workshop-tested parts, 10+ years with outboard engines
Same-day dispatch before 1 PM Mon–Fri via Royal Mail Tracked 24
Collection from Leigh, Greater Manchester. Workshop open Mon–Fri, 9 AM–5 PM
Technical support from experienced outboard specialists

6 HP 8 HP 9.9 HP 10 HP 15 HP 20 HP 25 HP Mercury Mariner Outboard 2 Stroke CDI Switch Box 855713A4