Mercury MerCruiser Fuel Cooler Kit – 8M0125846
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The Mercury MerCruiser 8M0125846 is the current OEM Cool Fuel pump and cooler kit for MerCruiser sterndrive and inboard engines equipped with the Gen II Cool Fuel system. It replaces the complete fuel pump and cooler assembly in one service kit, keeping fuel temperatures stable and fuel pressure consistent for the engine's EFI system — the right fix when vapor lock, fuel pressure drops, or a failed pump are causing issues on the water.
Compatible Applications
- MerCruiser 305 CID (5.0L) V8 sterndrive & inboard — Cool Fuel equipped
- MerCruiser 350 CID (5.7L) V8 sterndrive & inboard — Cool Fuel equipped
- MerCruiser 377 CID (6.2L) V8 — Cool Fuel equipped
- MerCruiser 454 CID (7.4L) V8 — Cool Fuel equipped
- MerCruiser 502 CID (8.2L) V8 — Cool Fuel equipped
- MerCruiser 496 CID engines — Cool Fuel equipped
- MerCruiser Black Scorpion models — Cool Fuel equipped
- Typical serial range: 0L000000 – 0M299999 (verify against your engine serial number before ordering)
Supersedes / Replaces
- 861156A02 — previous OEM part number
- 861156A01 — earlier OEM part number
- Sierra 18-8861 — aftermarket equivalent
Kit Contents
- Electric fuel pump
- Fuel cooler assembly
- O-rings and seals
- Fuel pressure regulator filter
- Mounting hardware and fittings
Product Details
- Part Number: 8M0125846
- Brand: Mercury Marine / Quicksilver
- Type: OEM Cool Fuel pump & cooler kit (Gen II)
- System: Cool Fuel EFI fuel delivery system
- Fitment: MerCruiser sterndrive and inboard engines with Cool Fuel — confirm via engine serial number
Technical FAQ
- What is the Cool Fuel system? Cool Fuel is MerCruiser's integrated fuel pump and cooler module that uses raw water or circulating coolant to keep fuel temperatures low in EFI applications, preventing vapor lock and protecting injectors in high-heat engine compartments.
- How do I know if my engine has a Cool Fuel system? Check your engine serial number against the MerCruiser parts diagram for your model year. Cool Fuel systems were fitted to most EFI MerCruiser V8 sterndrives and inboards from the mid-1990s through the mid-2000s.
- Is this a Gen II or Gen III kit? This is a Gen II Cool Fuel kit. For Gen III systems, see the Quicksilver Gen III Cool Fuel Filter Kit 35-13523 or the Mercury Gen III Cool Fuel Filter Disc 35-892665.
- What service interval applies? The Cool Fuel pump should be inspected at each seasonal service. Replace the full kit when fuel pressure is outside spec, the pump is noisy, or the cooler shows corrosion or leakage. Filter elements should be replaced annually.
Related Products
- Mercury MerCruiser Fuel Module Kit 8M0047215
- Quicksilver Gen III Cool Fuel Filter Kit 35-13523
- Mercury Gen III Cool Fuel Filter Disc 35-892665 / 8M0204703
- Mercury MerCruiser Quicksilver Fuel Pump Kit 866170A01
- Engineered Marine Products Fuel Filter Kit 35-13523-1
Parts Desk Insights
This kit is the correct choice when you are doing a complete Cool Fuel system overhaul on a Gen II MerCruiser EFI engine — replacing the pump and cooler together rather than just the filter. The most common reason customers need this kit is a fuel pump that has failed outright or a cooler that is leaking, corroded, or restricting flow. A key thing to watch: confirm your engine is a Gen II Cool Fuel application and not Gen III before ordering, as the two systems use different components entirely. If you only need the filter service components, the Quicksilver 35-13523 filter kit may be the more appropriate starting point for Gen III engines. Always cross-reference with your engine serial number — running the wrong fuel system components can cause hard starting, fuel pressure faults, or damage to injectors.
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.