Spark Plug Wire Kit 84-813720A5 503748 18-8800-1 for MerCruiser OMC Stern Drive
Spark Plug Wire Kit 84-813720A5 503748 18-8800-1 for MerCruiser OMC Stern Drive
Product Overview
Ignition spark plug wire kit for the MerCruiser and OMC sterndrive engines with conventional points ignition, the five wire set with four plug leads and a coil lead. It replaces MerCruiser 84-813720A5 and OMC 503748, it also crosses to Sierra 18-8800-1, CDI 631-0007 and Mallory 9-28020, and it ships as one set in a 210 mm x 120 mm x 60 mm box at 270 g.
Points ignition needs a different lead set from the later electronic systems. These are suppression leads with a wound stainless conductor, so they carry the spark without the radio interference that a plain copper core would put through the electronics on the boat.
The kit is four plug wires and one coil wire, which is the full set for a four cylinder engine. Leads that have gone hard at the boot end arc to earth, and the symptom is a misfire that gets worse in damp weather or a tingle from the engine cover when the engine is running.
Fitting a set is cheap maintenance on an older sterndrive. The wires on these engines run close to the exhaust manifolds, so the silicone jacket and boots are what keep them alive in a hot engine bay, and old leads that have gone brittle at the manifold are the usual failure.
Fitment covers the MerCruiser 110, 120 with the 153 cid four, 140 with the 181 cid four and the 3.0LX, plus the OMC 100, 110, 120 and 140 sterndrives and the 2.3 litre four cylinder from 1987 to 1990, all with points ignition. Check the engine model before ordering, because the later electronic ignition engines take a different set.
Specifications
| Specification | Detail |
|---|---|
| Condition | New / New with tags |
| Type | Ignition spark plug wire kit |
| MerCruiser Part Number | 84-813720A5 |
| Also Replaces | 84-816761Q5, 816761A5, 43376A5 |
| OMC Part Number | 503748 |
| Sierra Part Number | 18-8800-1 |
| CDI Part Number | 631-0007 |
| Mallory Part Number | 9-28020 |
| Conductor | Stainless steel wound core with Kevlar |
| Jacket | Silicone, high temperature rated |
| Suppression | RFI suppression for sensitive electronics |
| Fits | MerCruiser and OMC sterndrives with conventional points ignition |
| Quantity | 5 wires, four plug leads and one coil lead |
| Net Weight | 270 g including packaging |
| Pack Size | 210 mm x 120 mm x 60 mm |
| Pack Size In Inches | 8.27 in x 4.72 in x 2.36 in |
| Warranty | 3 year |
OEM Cross Reference
| Brand | Part Numbers |
|---|---|
| MerCruiser | 84-813720A5, 84-816761Q5 |
| MerCruiser | 816761A5, 43376A5 |
| OMC | 503748 |
| Sierra | 18-8800-1 |
| CDI | 631-0007 |
| Mallory | 9-28020 |
Compatible Engines
| Brand | Model | Displacement | Ignition |
|---|---|---|---|
| MerCruiser | 110 | Four cylinder | Points |
| MerCruiser | 120 | 153 CID | Points |
| MerCruiser | 140 | 181 CID | Points |
| MerCruiser | 3.0LX | Four cylinder | Points |
| OMC | 100 | Four cylinder | Points |
| OMC | 110 | Four cylinder | Points |
| OMC | 120 | Four cylinder | Points |
| OMC | 140 | Four cylinder | Points |
| OMC | 2.3 L | Four cylinder, 1987-1990 | Points |
What's Included
| Component | Detail | Qty |
|---|---|---|
| Spark plug wire | Plug leads with silicone boots, type 1 | 3 |
| Spark plug wire | Plug lead with silicone boots, type 2 | 1 |
| Coil wire | Coil to distributor lead | 1 |
| Distributor cap and rotor | Not included, inspect them before fitting new leads | 0 |
| Spark plugs | Not included, fit new plugs at the same time | 0 |
Packing Dimensions
| Measure | Millimetres | Inches |
|---|---|---|
| Pack length | 210 mm | 8.27 in |
| Pack width | 120 mm | 4.72 in |
| Pack height | 60 mm | 2.36 in |
| Weight with packaging | 270 g | 9.52 oz |
Signs The Leads Need Replacing
| What You See | What It Means | Action |
|---|---|---|
| Misfire in damp weather | Leads arcing through old boots | Fit the new set |
| Rough idle that clears at speed | One lead breaking down | Fit the new set |
| Tingle from the engine cover | Lead leaking spark to earth | Fit the new set |
| Brittle or cracked boots | Heat damage near the manifold | Fit the new set |
| Radio noise on the boat electronics | Suppression core failed | Fit the new set |
| Hard starting when warm | Weak spark from tired leads | Fit the new set and check the cap |
Fitting Notes
| Step | Action |
|---|---|
| 1 | Check the engine model and confirm points ignition |
| 2 | Disconnect the battery before touching the ignition circuit |
| 3 | Take one lead off at a time and match it with a new one of the same length |
| 4 | Check the distributor cap and rotor while the leads are off |
| 5 | Fit each new lead fully onto the cap tower and the plug |
| 6 | Route the leads away from the exhaust manifold |
| 7 | Start the engine and check it idles cleanly |
| 8 | Run it to temperature and check for arcing in the dark |
Condition & Warranty
| Item | Detail |
|---|---|
| Condition | New / New with tags |
| Warranty | 3 year |
| Packaging | Box, 210 mm x 120 mm x 60 mm |
Before You Buy
- Replaces MerCruiser 84-813720A5 and OMC 503748
- Also crosses to MerCruiser 84-816761Q5, 816761A5 and 43376A5
- Sierra 18-8800-1, CDI 631-0007, Mallory 9-28020
- Five wires, four plug leads and one coil lead
- Fits the MerCruiser 110, 120, 140 and 3.0LX with points ignition
- Fits the OMC 100, 110, 120, 140 and 2.3 L from 1987 to 1990
- 270 g with packaging, box 210 mm x 120 mm x 60 mm
- 30-Day Easy Returns
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Boat Owners' Review
Before You Buy
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