816761A5 Spark Plug Ignition Coil Wire Set fits Mercruiser 120 140 2.5L 3.0L GM Stern Drives 816761Q5 813720A5 816761K5
816761A5 Spark Plug Ignition Coil Wire Set fits Mercruiser 120 140 2.5L 3.0L GM Stern Drives 816761Q5 813720A5 816761K5 is backordered and will ship as soon as it is back in stock.
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Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
816761A5 Spark Plug Ignition Coil Wire Set fits Mercruiser 120 140 ...
Product Details
This aftermarket Spark Plug Wire Set is engineered for Mercruiser GM inline 4-cylinder engines, including 120, 140, 2.5L, and 3.0L models manufactured from 1983 to 1995, covering various sterndrive applications.
It serves as a direct interchange for a wide range of part numbers, including Mercruiser 816761A5 and 816761Q5, Sierra 18-8833-1, and Mallory 9-28020.
- Engineered as a direct replacement for a hassle-free installation.
- Constructed with a robust Kevlar core and high-temperature silicone insulation.
- Includes a complete set of 5 wires in factory-specified lengths.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket brands.
| Brand | Part Number |
|---|---|
| Mercruiser | 816761A5 |
| Mercruiser | 816761Q5 |
| Mercruiser | 813720A5 |
| Mercruiser | 816761K5 |
| Sierra | 18-8833-1 |
| CDI | 631-0007 |
| Mallory | 9-28020 |
| OMC | 503748 |
| HeuroFosh | 816761A5 |
Engine & Model Compatibility
Confirm your engine model and year in the table below. It is critical to check your engine's serial number to guarantee fitment.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercruiser | 120 GM 153 I/L4 | 120 | 4-Stroke | 1983–1986 | 816761A5 | Serial #6229718-0B531853 |
| Mercruiser | 140 GM 181 I/L4 | 140 | 4-Stroke | 1982–1986 | 816761A5 | Serial #6229718-0B450800 |
Technical Specs
- Product Type
- Marine Spark Plug Wire Set
- Installation
- Direct replacement
- Conductor
- Stainless Steel
- Core Material
- Kevlar
- Insulation Material
- Silicone
- Wire Lengths
- Varies: 17.9" (45.5cm), 14.2" (36cm), 12.1" (30.7cm), 11.6" (29.5cm)
- Connector Type
- Spark Plug Boot
- Temperature Rating
- High-temperature protection
- Package Dimensions
- 10.25" × 7.25" × 2.75" (260.4 × 184.2 × 69.9 mm)
- Weight
- 10.4 oz (0.295 kg)
What’s in the Box
The package includes a complete set of 5 spark plug wires:
- 1 x Spark Plug Wire (45.5cm / 17.9 inch)
- 1 x Spark Plug Wire (36cm / 14.2 inch)
- 2 x Spark Plug Wire (30.7cm / 12.1 inch)
- 1 x Spark Plug Wire (29.5cm / 11.6 inch)
Installation Notes
- Ensure the engine is completely cool and disconnect the negative battery terminal for safety.
- To avoid mixing up the firing order, replace one spark plug wire at a time. Note the routing of the old wire before removal.
- Firmly grasp the boot, twist it gently to break the seal, and pull to remove the wire from the spark plug.
- Disconnect the other end of the wire from the distributor cap or ignition coil.
- Lightly apply dielectric grease to the inside of the new wire's boots to protect against corrosion and ease future removal.
- Route the new wire correctly and press the boot firmly onto the spark plug until it clicks into place.
- Connect the other end to the corresponding terminal on the distributor cap or coil, ensuring a secure connection.
- Repeat the process for the remaining wires, matching new wire lengths to the old ones.
- Once all wires are replaced, reconnect the battery terminal.
- Start the engine and check for smooth operation.
Troubleshooting & FAQ
How do I know if this wire set fits my engine?
This set is designed for Mercruiser GM inline 4-cylinder engines (120, 140, 2.5L, 3.0L) from 1983–1995. Please refer to our Engine & Model Compatibility table and cross-reference your engine's model, year, and serial number before ordering.
Do the wires need to be installed in a specific order?
Yes. The set includes wires of different lengths corresponding to each cylinder's distance from the distributor. To ensure a proper fit and prevent timing issues, replace one wire at a time to maintain the correct firing order. Match the length of the new wire to the old one for each cylinder.
What are the signs of a failing spark plug wire?
Common symptoms include a rough engine idle, difficulty starting, engine misfires (especially under load), poor acceleration, and a noticeable decrease in fuel economy. Visible signs can include cracks, burns, or corrosion on the wire jacket or connectors.
How often should spark plug wires be replaced?
Replacement intervals vary based on use and conditions, but a general guideline is every 30,000 to 50,000 miles or during a major tune-up. We recommend inspecting them annually for any signs of wear or damage.
What is the advantage of a Kevlar core and silicone insulation?
The Kevlar core provides exceptional strength, preventing breakage or stretching during installation and use. The dual-layer silicone jacket offers superior protection against high engine temperatures, oil, moisture, and abrasion, ensuring reliable voltage delivery and long service life.
Is there a difference in performance compared to OEM wires?
Our aftermarket wires are built to meet or exceed OEM specifications. They use high-quality materials like a stainless steel conductor, Kevlar core, and silicone insulation to deliver reliable spark and withstand the harsh marine environment, ensuring performance comparable to original parts.
Is this an OEM part?
This listing is for an aftermarket replacement, not an OEM component. It is built to OEM-level specifications with comparable materials and manufactured in an ISO 9002 facility, with batch inspections for consistency.
What are the shipping speed and cost?
We ship worldwide quickly—typical transit is 5–15 days. Standard shipping is free to most regions; expedited options will appear at checkout where available.
What is the warranty and return policy?
This product is covered by a 1-year warranty against manufacturing defects under normal use. If any issues arise, please contact our support team with your order details. Returns are accepted within our standard window for items that are unused and in their original condition. See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
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