Mercury 18545A1 Power Trim Pump Repair Kit — Oildyne MerCruiser Sterndrive
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Mercury 18545A1 — Power Trim Pump Repair Kit, Oildyne
| Part Number | 18545A1 |
|---|---|
| Brand | Mercury / Quicksilver (OEM) |
| Product Type | Power Trim Pump Overhaul Repair Kit |
| System | Oildyne Power Trim Pump — MerCruiser Sterndrive |
| Supersedes | 18545 |
| Weight | approx. 300 g |
Overview
Mercury 18545A1 is a genuine OEM power trim pump overhaul repair kit for MerCruiser sterndrive applications that use the Oildyne-style power trim pump. It contains the internal seals, O-rings, and components needed to rebuild the pump when it is leaking, losing pressure, or cycling poorly. This is a pump rebuild kit — not a complete pump assembly. Confirm that your trim system uses the Oildyne pump design before ordering.
Supersession
- Current part number: 18545A1
- Supersedes: 18545
- If your service records or parts diagram show 18545, 18545A1 is the correct current replacement.
Compatible Applications
- MerCruiser sterndrive applications equipped with the Oildyne-style power trim pump
- Internal pump rebuild when trim pump is leaking fluid, losing hydraulic pressure, or failing to hold trim position
- Overhaul of the Oildyne pump during trim system service or reseal
- Always confirm fitment by engine/drive model and serial number using the Mercury parts catalog before ordering — trim pump designs vary by model year and serial range
When This Kit Is Needed
- Trim pump leaking hydraulic fluid externally or internally
- Trim system losing pressure and not holding position (engine trims down under load)
- Trim pump cycling continuously without building pressure
- During a full trim system overhaul or reseal service
- Preventive rebuild when the pump is disassembled for inspection and seals are aged or hardened
Installation Notes
- Confirm your trim system uses the Oildyne pump design before disassembly — trim pump internal components vary by pump type and are not interchangeable between designs
- Reference the correct Mercury parts diagram for your engine model and serial number before ordering
- Drain and contain trim fluid before disassembly — use appropriate marine trim fluid when refilling
- Inspect the trim pump motor, reservoir, and hydraulic lines while the pump is apart; replace any other worn components at the same time to avoid a return service
- Bleed the trim system after reassembly to remove air from the hydraulic circuit before testing
Technical FAQ
- What is the Oildyne pump? The Oildyne is a specific style of hydraulic power trim pump used on many MerCruiser sterndrive applications. It is a self-contained hydraulic unit with an integral reservoir and electric motor. Not all MerCruiser trim systems use the Oildyne design — confirm your pump type before ordering this kit.
- My engine trims down on its own — is this the right kit? Trim drift (the engine slowly trimming down under load) is a common symptom of internal pump seal failure. This kit addresses the internal seals of the Oildyne pump. However, trim drift can also be caused by leaking trim cylinders — confirm the leak source before ordering a pump rebuild kit vs. a cylinder seal kit.
- Can I rebuild the pump myself? Trim pump rebuilds require careful attention to cleanliness and correct reassembly. If you have the Mercury service manual for your model, the rebuild procedure is documented. If in doubt, a marine service shop with MerCruiser experience is the safest option.
- What fluid does the Oildyne pump use? MerCruiser Oildyne trim systems use Mercury Power Trim and Steering Fluid (or approved equivalent). Do not use automotive transmission fluid or brake fluid.
Parts Desk Insights
Best Use Case: This kit is the right call when a customer has confirmed the Oildyne pump is the source of a leak or pressure loss, and they’re ready to rebuild rather than replace the whole pump assembly. It’s most commonly ordered alongside trim fluid and a reservoir O-ring when doing a complete pump service in one visit.
Common Issues: The most frequent mistake is ordering a pump repair kit without first confirming whether the leak is in the pump itself or in the trim cylinders. A cylinder O-ring leak looks similar from the outside but needs a different kit entirely — see the Mercury MerCruiser Trim Cylinder O-Ring Kit 87400A2. The second common issue is ordering this kit for a trim pump that is not the Oildyne design — always confirm pump type by model and serial number first.
Related Products
- Mercury MerCruiser Trim Cylinder O-Ring Kit 87400A2
- Mercury MerCruiser Trim Pump Reservoir Screw O-Ring Spacer 18527
- ARCO 6218 Mercury / MerCruiser Tilt & Trim Motor — 12V Oildyne (Motor Only)
- Sierra Tilt/Trim Hydraulic Reservoir — Mercury & MerCruiser | 47-6771
- Sierra Hydraulic Trim Pump Assembly with Steel Bracket — MerCruiser 1983+ | 47-6752
- Sierra Power Trim Relay — Mercury & MerCruiser | 47-5729
- Mercury MerCruiser Quicksilver Solenoid 8M0185622
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.