OVERSTOCKDIRECT NGK Laser Iridium Spark Plug 5887 — 6-Pack for Mercury/Mercruiser, Long-Life Marine Ignition

High-performance NGK IZFR5G Laser Iridium spark plugs (part 5887) — a six-pack designed to fit many Mercury/Mercruiser outboard and sterndrive engines requiring long-life, reliable ignition. These NGK Laser Iridium plugs from OVERSTOCKDIRECT are engineered to meet or exceed OEM fit and function for a broad range of Mercury Mercruiser marine engines and several Optimax/DFI/DFI M2/PRO XS models. Each plug uses a fine-wire iridium center electrode and a platinum ground tip, plus trivalent metal plating, to resist corrosion and make installation and removal smoother in marine environments. The technical specifications — 0.750" reach, 14 mm thread diameter, 5/8" hex, .032" pre-gap (0.8 mm), 5000 ohm resistor — match many factory requirements while delivering the durability demanded by saltwater and high-load conditions.

Which Mercury and Mercruiser models will these plugs fit?

These NGK IZFR5G plugs are compatible with a long list of Mercury Mercruiser engines across model years. Fitment covers numerous DFI and DFI M2 powerheads and pumps, V‑135, V‑150, V‑175, 200/225/250 DFI/PRO XS ranges, and many 115–225 hp Optimax units from 2003 and up where the OE specifies this part type.

• Works with many 200 DFI, 250 DFI, V‑135/150/175, 200XS DFI and 115–225 hp Optimax models
• Check serial ranges in your service manual for exact compatibility
• Flat seat, 14.0 mm thread diameter and 0.750" reach match common factory specs

What materials and design features improve spark life and reliability?

The center electrode uses a fine-wire iridium alloy for high melting point and minimal wear, while the ground electrode tip carries a platinum insert unless an alternate OE spec is required. Trivalent metal plating protects the threads and hex from corrosion and seizing, which is particularly valuable in marine service.

• Iridium center electrode for consistent spark and extended service life
• Platinum ground tip increases ignitability and durability
• Trivalent plating reduces corrosion and eases later removal

How do these plugs affect installation and engine performance?

These plugs are machined to OE-equivalent tolerances with a crush washer, 5/8" hex for standard tools, and a pre-gap of .032" (0.8 mm). The integrated 5000-ohm resistor and non-removable nut electrical terminal meet ignition system requirements while limiting radio interference, and the long-projection design supports stable combustion in modern engines.

• Pre-gapped to .032"; fine-wire center electrode supports crisp ignition
• 5/8" hex and crush washer included for straightforward installation
• Resistor type reduces RF interference for sensitive electronics

How should I maintain and replace these spark plugs on my boat?

Inspect plugs at recommended service intervals and replace them in sets to preserve balanced firing across cylinders. Look for consistent color and electrode wear; heavy deposits or irregular gaps indicate further engine or fuel-system attention is needed.

• Replace in full sets to maintain even performance across cylinders
• Torque to manufacturer spec and reuse the crush washer per guidance
• Store spares in a dry place and avoid cross-threading during installation

Who is this for These 6-pack NGK IZFR5G Laser Iridium plugs are aimed at marine owners, professional mechanics, and DIY technicians who maintain Mercury Mercruiser, Optimax, and related DFI outboard and sterndrive engines. Choose this set if you need OE-equivalent fitment, corrosion-resistant plating for marine conditions, long-life iridium performance, and a plug spec that matches many 115–250 hp engines. Always verify engine serial ranges and OEM recommendations before purchasing to ensure an exact match.

FAQ

Q: Are these NGK IZFR5G plugs compatible with 2003 Optimax 115–225hp?

A: Yes — they fit many 2003-up Optimax 115–225 hp models, but confirm your engine serial range against the listed fitment.

Q: Do these plugs require a special gap or tool for installation?

A: No special tool: use a 5/8" socket and torque to spec; they are pre-gapped to .032" (0.8 mm).