Mercury Quicksilver Water Separating Fuel Filter Kit 18458Q4 – Blue Sensor
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Overview
Part Number: 18458Q4 (service format: 35-18458Q4)
Brand: Quicksilver / Mercury Marine
Official Product Type: Water Separating Fuel Filter Kit
Supersedes: 35-18458A4, 35-184585
GTIN: 745061038233
System: Under-Cowl Fuel System — Water-Separating Fuel Filter
The Quicksilver 18458Q4 is the genuine OEM replacement water-separating fuel filter kit for 1996 and newer Mercury and Mariner V6 EFI outboards. Mercury specifies this as a 10-micron water-separating filter designed to remove fuel-borne contaminants, particles, and water before they reach the fuel-injection system. The kit includes the replacement filter element, sealing O-ring, and blue screw-in water-warning sensor — the sensor colour is the key distinction between this kit and other 18458-series filters.
Kit Contents
- 10-micron water-separating filter element (internal epoxy coating)
- Sealing O-ring
- Blue screw-in water-warning sensor
Key Features
- Genuine Quicksilver / Mercury Marine OEM replacement kit
- 10-micron filtration — removes water, particles, and contaminants from fuel
- Blue screw-in water-warning sensor included
- Internal epoxy coating and corrosion-resistant exterior
- Designed for under-cowl installation on applicable V6 EFI/DFI outboards
- GTIN: 745061038233
Compatible Applications
- Mercury V6 EFI outboards, 1996 and newer (selected serial ranges)
- Mariner V6 EFI outboards, 1996 and newer (selected serial ranges)
- Mercury OptiMax 135 HP (selected serial ranges)
- Mercury OptiMax 150 HP (selected serial ranges)
- Mercury OptiMax 175 HP (selected serial ranges)
- Mercury 150 Pro XS (selected serial ranges)
- Selected additional Mercury V6 EFI / DFI applications — confirm by serial number
Serial Number & Sensor Fitment Notice
Confirm the complete outboard model and serial number before ordering. Mercury used different water-separating filter kits depending on fuel-system generation and water-sensor configuration. The 18458Q4 uses the blue screw-in water-warning sensor. Do not substitute with 18458Q3, which uses a different sensor configuration and is not interchangeable.
Dimensions & Weight
- Weight: Approx. 0.10 kg (0.22 lb)
- Packed dimensions: Estimated approx. 12 cm × 8 cm × 8 cm
Service Interval
Mercury recommends replacing this filter:
- Every 100 operating hours, or
- Annually, including during seasonal lay-up / winterization service
Follow the specific maintenance schedule in your engine owner’s manual if it specifies a different interval. Earlier replacement is appropriate if there is evidence of water contamination, restricted fuel flow, deteriorated filter condition, or a water-in-fuel warning light.
Installation Notes
- Filter is located under the engine cowl on applicable Mercury and Mariner V6 EFI/DFI outboards
- Replace the sealing O-ring supplied with the kit at every filter change
- Inspect the sensor threads and electrical connection before installing the new sensor
- Install the supplied blue water-warning sensor into the replacement filter body
- Check carefully for fuel leaks after installation before starting the engine
- Prime or restore the fuel system according to the applicable Mercury service procedure
Superseded / Alternate Part Numbers
- Current: 18458Q4 / 35-18458Q4
- Supersedes: 35-18458A4
- Supersedes: 35-184585
- Service progression: 35-18458A4 → 35-18458Q4 | 35-184585 → 35-18458Q4
Manufacturer Reference
Mercury Marine maintains an official product listing for this kit. Search 18458Q4 on the Mercury Marine website to access the current product page and associated documentation.
Technical FAQ
Q: What is the difference between 18458Q4 and 18458Q3?
A: Both are water-separating fuel filter kits in the same series, but they use different water-warning sensor configurations. The 18458Q4 includes the blue screw-in sensor. The 18458Q3 uses a different sensor setup and the two are not interchangeable. Match the filter kit to the sensor type already installed in your engine’s fuel system.
Q: Does this kit include the O-ring?
A: Yes. The 18458Q4 kit includes the replacement filter element, sealing O-ring, and blue water-warning sensor. Replace the O-ring at every filter change to ensure a proper fuel-tight seal.
Q: How do I know when the filter needs to be replaced early?
A: Replace the filter early if the water-in-fuel warning light activates, if you notice reduced engine performance or fuel flow, or if the filter element appears discoloured or contaminated during inspection. Fuel quality and storage conditions can shorten filter life even within the 100-hour interval.
Parts Desk Insight
The most common ordering mistake with the 18458-series filters is selecting the wrong sensor version. The Q4 and Q3 kits look similar, but the sensor types are not interchangeable — installing the wrong sensor can prevent the water-warning system from functioning correctly. If a customer is replacing a filter on an engine they’re not familiar with, confirming the existing sensor colour (blue for Q4) before ordering saves a return trip. At annual service or winterization, this is a straightforward maintenance item that’s easy to include alongside an oil change or gear lube service.
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.