MerCruiser Distributor Cap & Rotor Kit 805759Q3 | GM V8 Thunderbolt IV & V
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Distributor Cap & Rotor Kit — Part 805759Q3
| Part Number | 805759Q3 |
|---|---|
| Brand | Mercury Marine / MerCruiser / Quicksilver |
| Official Product Type | Distributor Cap and Rotor Kit |
| System | Ignition — Thunderbolt IV / Thunderbolt V HEI Distributor |
| Kit Contents | Distributor cap, rotor, and cap gasket |
| Cap Construction | PBT/PET plastic with solid brass terminal inserts |
| Related Mercury Reference | 805759T3 |
| Aftermarket Cross-Reference | Sierra 18-5273, GLM 71780, CDI Electronics E66-0012 |
This is the genuine OEM distributor cap and rotor kit for marinized GM V8 MerCruiser engines equipped with Thunderbolt IV or Thunderbolt V HEI ignition systems. The kit includes the distributor cap, rotor, and cap gasket — everything required for a complete distributor service on applicable engines.
The cap uses PBT/PET plastic construction for heat and warpage resistance, with solid brass terminal inserts to resist corrosion and electrical pitting. It is also designed to reduce RFI interference with onboard electronics — an important consideration in the marine environment.
Ignition system identification matters: MerCruiser used multiple HEI distributor designs on similar GM V8 engines. The 805759Q3 kit is specifically for the Thunderbolt IV and Thunderbolt V family. It is not the same kit used on later Delco HEI distributors. Confirm your distributor type before ordering.
Part Number Reference
- Current OEM kit number: 805759Q3 (Quicksilver) / 805759T3 (Mercury equivalent)
- Earlier cap references: 805759T1, 805759A5, 805759A2, 16457A4
- Rotor references: 13524T1, 13524A5, 13524A1
- Aftermarket: Sierra 18-5273, GLM 71780, CDI Electronics E66-0012
Compatible Applications
Fitment is by ignition system type, not displacement alone. Confirm the distributor is a Thunderbolt IV or Thunderbolt V HEI unit before ordering. Verify by engine serial number and ignition diagram.
- 5.0L / 305 CID V8 — Selected MerCruiser applications with Thunderbolt IV or Thunderbolt V HEI distributor
- 5.7L / 350 CID V8 — Selected MerCruiser applications with Thunderbolt IV or Thunderbolt V HEI distributor
- 7.4L / 454 CID V8 — Selected MerCruiser applications with Thunderbolt IV or Thunderbolt V HEI distributor
- 8.2L / 502 CID V8 — Selected MerCruiser applications with Thunderbolt IV or Thunderbolt V HEI distributor
When This Part Needs Replacement
- Distributor cap contacts are burned, pitted, or showing visible arcing damage
- The cap is cracked or has carbon tracking between terminals
- Corrosion or green oxidation is visible on the cap terminals
- The rotor contact is worn, burned, or corroded
- The engine has an ignition miss that has been traced to the distributor
- Hard starting or rough running is confirmed to be caused by degraded cap or rotor
- Scheduled ignition tune-up calls for cap and rotor replacement
Related Parts
- Mercury MerCruiser Distributor Cap Gasket 27-805760 — cap gasket (also included in this kit)
- Mercury Distributor Cap & Rotor Kit 805759T3 — Mercury-branded equivalent kit
- Arco DR004 Distributor Rotor — MerCruiser Thunderbolt V8 5.0 / 5.7 / 7.4L — aftermarket rotor alternative
- Mercury Quicksilver 898253T23 Distributor Cap — MerCruiser 4.3L V6 MPI — V6 MPI application (different system)
Installation Notes
- Mark or photograph spark plug wire positions before removing the old cap
- Transfer wires one at a time where possible to avoid misfiring order
- Inspect the distributor housing interior for moisture, corrosion, or carbon tracking
- Check ignition wires for cracked insulation or damaged terminals — replace if needed
- Install the supplied cap gasket correctly to seal the housing
- Confirm the rotor is fully seated and oriented correctly before installing the cap
- Verify correct firing-order wire placement before starting the engine
Parts Desk Insights
Most common customer issue: Ordering this kit based on engine displacement without confirming the ignition system. MerCruiser used Thunderbolt IV, Thunderbolt V, and Delco HEI distributors across similar GM V8 engine families at different production years. The cap and rotor dimensions are different between these systems — the 805759Q3 kit fits the Thunderbolt IV/V family only. If you’re not sure which distributor your engine has, check the ignition diagram for your engine serial number range or send us the serial number before ordering.
Best use case: Ideal for scheduled ignition tune-ups on Thunderbolt IV/V-equipped MerCruiser V8 engines, or when diagnosing an ignition miss, hard starting, or rough idle that has been traced to the distributor. The kit format covers the full distributor cap service — cap, rotor, and gasket — in one order.
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.