Mercury Mariner Outboard Ignition Coil | RECMAR 300-08310

Recmar Ignition Coil | 300-08310 | Mercury Mariner V6 2.5L 3.0L DFI Optimax | 1998–2006

The ignition coil on a Mercury or Mariner V6 DFI outboard transforms low-voltage battery current into the high-voltage pulse the spark plug needs to fire — up to 40,000 volts per firing event. When a coil begins to fail, it typically does so intermittently before failing completely: misfires at idle that clear at speed, cylinder dropouts under load, rough running when the engine is hot, and eventually a dead cylinder that doesn't respond to plug replacement. The Recmar #300-08310 is an aftermarket replacement ignition coil engineered to meet or exceed OEM specifications for Mercury and Mariner 6-cylinder 2.5L and 3.0L DFI outboards from 1998 through 2006, including EFI 200, Optimax, and Sport Jet models. Backed by a 2-year manufacturer warranty.

Replaces Mercury 339-850227 and 339-856991 — also replaces Sierra 18-5187, ARCO IG012, and CDI 184-0005.

Part Details:

• Part Number: 300-08310 (Recmar)
• SKU: RECMAR-REC300-08310
• Manufacturer: Recmar (aftermarket)
• Type: Ignition Coil
• Fits: Mercury and Mariner 6-cylinder 2.5L and 3.0L DFI outboards, 135–225 HP, 1998–2006 — including EFI 200, Optimax, and Sport Jet models
• Replaces Mercury: 339-850227, 339-856991
• Replaces Sierra: 18-5187
• Replaces ARCO: IG012
• Replaces CDI Electronics: 184-0005
• Warranty: 2-year manufacturer warranty
• Condition: New
• Country of Origin: USA

Additional Information

Diagnosing Ignition Coil Failure on Mercury Optimax and DFI Outboards:

Mercury V6 DFI and Optimax engines use individual coils — one per cylinder — so a failing coil produces a single-cylinder misfire rather than a complete no-start. This makes diagnosis more precise but also means the misfire can be subtle, especially at lower RPM where the other five cylinders can partially mask the dropout. Key diagnostic indicators:

• Cylinder-specific misfire — swap the suspected coil with an adjacent coil and check if the misfire moves to the new cylinder location; if it does, the coil is confirmed bad
• Heat-related dropout — coils that fail when hot but recover when cool have insulation breakdown; they will test good cold and only show the fault at operating temperature
• Resistance testing — primary and secondary winding resistance can be checked with a multimeter; compare against the specification in your Mercury service manual; open or out-of-spec resistance confirms a bad coil
• Spark test — a coil producing weak or intermittent spark on a spark tester confirms it needs replacement even if resistance tests borderline

Aftermarket vs. OEM — What to Expect from Recmar:

Recmar is an established marine aftermarket parts manufacturer with a reputation for meeting OEM specs on ignition components. The 300-08310 is backed by a 2-year warranty — longer than many OEM ignition components. For a V6 DFI outboard where you have six coils and are replacing one or two, the Recmar offers a meaningful cost advantage over Mercury OEM pricing while delivering equivalent ignition performance in normal service. If your engine is under dealer warranty or you require OEM certification, use the Mercury OEM coil instead.

Frequently Asked Questions

1. How do I confirm this coil fits my Mercury or Mariner outboard?
The Recmar 300-08310 fits Mercury and Mariner 6-cylinder 2.5L and 3.0L DFI outboards from 1998–2006 in the 135–225 HP range, including EFI 200, Optimax, and Sport Jet models. Cross-reference your engine's model and serial number against the Mercury parts catalog, or verify that your current coil carries one of the OEM part numbers this unit replaces: Mercury 339-850227 or 339-856991. Contact us at MacombMarineParts.com with your engine model and serial number if you need fitment confirmed before ordering.

2. Should I replace all six coils at once or just the failed one?
If one coil has failed on a high-hour engine, the others are the same age and have accumulated the same thermal cycles. Replacing all six at once is the more economical approach when labor is involved — you pay for the job once rather than pulling the powerhead multiple times as the remaining coils fail in sequence. If the engine is relatively low-hours and only one coil has failed, replacing the single failed coil is reasonable. The 2-year warranty on the Recmar coils supports either approach.

3. What is the correct torque spec for installing ignition coils on a Mercury V6 DFI outboard?
Refer to your Mercury or Mariner outboard service manual for the torque specification for ignition coil mounting fasteners on your specific engine. Torque specs vary across engine families and model years — do not assume a spec from another engine model. Over-torquing coil mounting hardware can crack coil bodies or strip threads in the powerhead.

4. Can I test my existing coil before replacing it?
Yes — measure primary winding resistance between the coil's positive and negative terminals, and secondary resistance between the high-voltage output and the negative terminal. Compare your readings against the specification in your Mercury service manual. A coil reading open circuit or significantly out of spec on either winding should be replaced. Note that a coil can test within spec cold and still fail when hot — if resistance tests pass but misfire symptoms persist, perform a hot-soak test or swap the coil to another cylinder to confirm.