Mercury / Quicksilver 808483T3 Distributor Cap | MerCruiser GM V8 Delco HEI | 350 MAG / 454 EFI
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Part Details
- Part Number: 808483T3
- Brand: Mercury Marine / Quicksilver (Genuine OEM)
- Official Product Type: Distributor Cap — Delco HEI, GM V8
- Ignition System: Delco HEI — GM-based MerCruiser V8
- Distributor Assembly Reference: 805222A1
- Cap Construction: PBT/PET plastic — warp- and thermal-crack resistant
- Terminals: Solid brass — corrosion-resistant; reduced radio-frequency interference
- Supersedes: 808483, 808483T
- Important: Does NOT fit MPI engines with ECM 555 connectors
- Sierra Aftermarket Cross-Reference: 18-5354
- GLM Aftermarket Cross-Reference: 71400
- Mallory Aftermarket Cross-Reference: 9-29411
- GTIN / UPC: 745061043367
- Weight (approx.): 200 g
What This Part Is
Mercury / Quicksilver 808483T3 is a genuine OEM replacement distributor cap for selected GM-based MerCruiser V8 engines using the Delco HEI ignition system. The cap is the current production replacement for earlier Mercury 808483 and 808483T references and is designed to fit distributor assembly 805222A1. The PBT/PET housing resists warping and thermal cracking, and the solid brass terminals are designed to reduce both corrosion and radio-frequency interference with onboard electronics.
Critical fitment note: Mercury specifically excludes MPI engines with ECM 555 connectors from this application. 808483T3 is for the Delco HEI distributor configuration only. It is not interchangeable with Thunderbolt IV/V caps, later flat-cap Vortec distributor caps, or V6 distributor applications. Verify the distributor type and engine serial number before ordering.
If the rotor also requires replacement, 808483K1 is the complete cap-and-rotor service kit for applicable Delco HEI V8 systems.
Compatible Applications
Fitment must be confirmed by engine model, serial number, and installed distributor type. Documented MerCruiser applications include:
- MerCruiser 350 MAG EFI — Delco HEI ignition (confirm serial number)
- MerCruiser 350 MAG MPI — Delco HEI ignition only; not ECM 555 MPI versions
- MerCruiser 350 MAG Ski — Delco HEI ignition (confirm serial number)
- MerCruiser 454 EFI — Delco HEI ignition (confirm serial number)
- Other GM V8 MerCruiser engines where parts diagram calls for 808483T3 with distributor assembly 805222A1
Does not fit: MPI engines with ECM 555 connectors, Thunderbolt IV/V distributor applications, later Vortec flat-cap configurations, or V6 engines.
When to Replace
Replace the distributor cap if inspection shows any of the following:
- Burned, eroded, or heavily corroded terminals
- Carbon tracking inside the cap body
- Cracks in the cap housing
- Moisture or corrosion inside the distributor
- Intermittent ignition misfire
- Hard starting or rough running traced to secondary ignition
- Visible arcing at the cap or plug-wire terminals
The distributor cap is a normal ignition wear item and should be inspected at every tune-up service alongside the rotor, spark plugs, and plug wires.
Service Interval
Inspect the distributor cap annually or at every major ignition service. Replace at the first sign of carbon tracking, terminal corrosion, or cracking — do not defer if any of those conditions are present. On marine engines with seasonal use, cap inspection at spring commissioning is good practice.
Installation Notes
- Disconnect battery power before servicing the ignition system
- Mark or photograph spark-plug wire positions on the old cap before removal
- Transfer plug wires one at a time to maintain the correct firing order
- Inspect the rotor at the same time — if worn or burned, replace it; consider 808483K1 cap-and-rotor kit to replace both together
- Inspect spark-plug wire boots and terminals for cracking or corrosion
- Ensure all plug-wire terminals are fully seated in the new cap
- Secure the cap evenly with the correct distributor-cap retaining screws
- Confirm the engine starts cleanly and runs without misfire before returning to service
- Follow the MerCruiser service procedure for the specific engine and distributor
Technical FAQ
How do I know if my engine uses the Delco HEI distributor vs. a Thunderbolt or ECM 555 system?
The Delco HEI distributor cap on GM V8 MerCruiser engines is a large round cap with external plug-wire towers around the perimeter and a central coil. Thunderbolt IV/V distributors use a different cap profile. ECM 555 MPI systems use a different ignition configuration entirely. The most reliable way to confirm is to check the distributor cap part number in the ignition diagram for your engine’s serial number — if 808483T3 or distributor assembly 805222A1 appears, the Delco HEI configuration is installed.
What is the difference between 808483T3 (this cap) and the 808483K1 kit?
808483K1 is a complete kit that includes both the distributor cap and rotor. 808483T3 is the cap only. If both the cap and rotor are due for replacement — which is typical during a full tune-up — order the 808483K1 kit instead.
What part numbers does 808483T3 supersede?
808483T3 is the current production number and supersedes 808483 and 808483T. Order by 808483T3 when replacing any of those earlier numbers.
What aftermarket part numbers cross-reference to 808483T3?
Documented aftermarket equivalents include Sierra 18-5354, GLM 71400, and Mallory 9-29411. Verify any cross-reference against the current OEM diagram for your engine before substituting.
Will this cap reduce interference with my VHF radio or chartplotter?
Yes — Mercury specifies that 808483T3 is designed to reduce radio-frequency interference (RFI) from the ignition system, which can affect VHF radios, GPS, and other onboard electronics. Using the OEM cap helps maintain suppression performance.
Superseded / Cross-Reference Part Numbers
- Current Mercury OEM: 808483T3
- Superseded by 808483T3: 808483, 808483T
- Sierra aftermarket: 18-5354
- GLM aftermarket: 71400
- Mallory aftermarket: 9-29411
- GTIN / UPC: 745061043367
Related Parts
- Mercury / Quicksilver 808483K1 Distributor Cap & Rotor Kit — complete cap-and-rotor service kit for applicable Delco HEI V8 engines
- Browse Ignition Components for all distributor caps, rotors, and ignition service parts
- Browse Engine Electrical for spark-plug wire sets and related electrical components
- Browse MerCruiser Marine Engine Parts
Parts Desk Insights
Best use case: 808483T3 is the correct cap when only the distributor cap needs replacement on a GM V8 MerCruiser with Delco HEI ignition — for example, when the cap shows carbon tracking or terminal corrosion but the rotor is still in good condition. For a full ignition tune-up where both the cap and rotor are being replaced, the 808483K1 kit is the more efficient order.
Common issue: The most frequent mistake is ordering 808483T3 for a MerCruiser 350 MAG MPI engine that uses the ECM 555 connector — Mercury explicitly excludes those applications. The cap fits the Delco HEI distributor family only. Always verify the distributor style and confirm the engine serial number does not fall into the ECM 555 MPI category before ordering. A second common issue is ordering the cap alone when the rotor is also worn — inspect the rotor while the cap is off and order the 808483K1 kit if both need replacement.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 1-3 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.