Mercury Quicksilver Carburetor Diaphragm Kit 857005A1
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Mercury Quicksilver Carburetor Diaphragm Kit — 857005A1
| Part Number | 857005A1 | Mercury Catalog: 21-857005A1 |
| Brand | Mercury Marine / Quicksilver |
| Official Product Type | Carburetor Diaphragm Repair Kit |
| Kit Contents | 12-piece set — fuel-pump diaphragms, gaskets, check valves, spring, cap, and screws |
| System | Fuel / Carburetor |
| Engine Family | Mercury & Mariner 2-stroke outboards |
| GTIN / Barcode | 745061440685 |
Compatible Applications
Mercury officially rates 857005A1 for selected 30–65 HP Mercury and Mariner 2-stroke outboards. Exact fitment depends on carburetor and fuel-pump configuration. Confirm by engine horsepower, model year, serial number, and parts diagram before ordering.
- 30 HP Mercury & Mariner 2-stroke outboards (selected models)
- 40 HP Mercury & Mariner 2-stroke outboards (selected models)
- 50 HP Mercury & Mariner 2-stroke outboards (selected models)
- 60 HP Mercury & Mariner 2-stroke outboards (selected models)
- 65 HP Mercury & Mariner 2-stroke outboards (selected models)
Serial Number & Diagram Fitment
Mercury used multiple diaphragm-kit configurations across similar 2-stroke outboards. Always verify by engine model, serial number, and the carburetor/fuel-pump parts diagram — not by appearance alone. If you have your serial number, contact us and we will confirm fitment before you order.
Superseded / Legacy Part Numbers
857005A1 is the current replacement for the following earlier kit numbers:
- 42990A8
- 42990A10
- 42990A11
Additional 42990A-series numbers may also cross to 857005A1 depending on application.
When to Replace the Diaphragm Assembly
Consider a full rebuild when you notice any of the following:
- Hard starting or failure to start
- Fuel starvation at speed
- Hesitation or stumble during acceleration
- Poor high-speed fuel delivery
- Irregular idle
- Loss of power under load
- Fuel leakage at the diaphragm section
- Hardened, torn, or distorted diaphragm material
Installation Notes
- Clean the carburetor body thoroughly before disassembly
- Note the order and orientation of diaphragms, gaskets, and check valves
- Replace the entire soft-parts set — do not reuse hardened or compressed components
- Inspect mating surfaces for corrosion or distortion before reassembly
- Inspect fuel hoses and connections while the assembly is apart
- Follow the Mercury service manual for your specific engine serial range
Related Parts
- Mercury Carburetor Fuel Pump Diaphragm 16275
- Mercury MerCruiser Quicksilver Carburetor Fuel Pump Diaphragm 16325
- Mercury Carburetor Fuel Pump Cover Gasket 27-16274
- Mercury MerCruiser Quicksilver Diaphragm Kit 55278A1
Parts Desk Insights
This is the kit to reach for when a 30–65 HP 2-stroke Mercury or Mariner is showing fuel-delivery symptoms — hard starting, hesitation, or lean-running conditions are the most common complaints we see linked to a worn diaphragm on these engines. Because Mercury supplies the complete 12-piece soft-parts set together, a full rebuild is more reliable than sourcing individual components separately. Match by the engine parts diagram first, then confirm with the serial number — the same horsepower range can carry different carburetor assemblies across production years.
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.