Sierra 9251 Outboard Maintenance Kit | Mercury 75–115 HP Optimax 1.5L 2-Stroke (S/N 1B227000+)
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Everything You Need for a Full Mercury Optimax Service — One Kit.
The Sierra 9251 Outboard Maintenance Kit is a complete, one-box service solution for Mercury 75, 90, and 115 HP Optimax 1.5L 2-stroke outboard engines with serial numbers 1B227000 and up. All components are specifically engineered for this engine family — no guessing on compatibility, no sourcing parts separately.
Sierra maintenance kits are designed to cover all the critical service items at the recommended maintenance interval, so you can complete a full tune-up in a single session with everything pre-selected and ready to install.
Kit Contents (47-9251)
- Impeller
- Water pump repair kit
- Thermostat
- Thermostat gasket and bolt
- Fuel filter
- Inline oil filter
- Anode (aluminum)
- Anode mounting bolt
Key Features
- All components engineered specifically for Mercury 75–115 HP Optimax 1.5L 2-stroke outboards
- Aluminum anodes for corrosion protection in saltwater and freshwater environments
- Water pump impeller and repair kit included — the most critical service item for outboard longevity
- Fuel and oil filters included for a complete fluid system service
- Thermostat and gasket included to ensure proper engine temperature regulation
Compatible Applications
- Mercury 75 HP Optimax 1.5L 2-stroke outboard — serial numbers 1B227000 and up
- Mercury 90 HP Optimax 1.5L 2-stroke outboard — serial numbers 1B227000 and up
- Mercury 115 HP Optimax 1.5L 2-stroke outboard — serial numbers 1B227000 and up
- Confirm your engine serial number before ordering to ensure correct kit selection
Parts Desk Insights
The 9251 kit is the right buy when you're doing a scheduled service on a Mercury Optimax 1.5L and want to handle the water pump, thermostat, anodes, and filters in a single order. The impeller is the most time-sensitive item in this kit — Mercury recommends replacing it every 300 hours or 3 years, whichever comes first, and a failed impeller can cause catastrophic overheating in minutes. If you're already pulling the lower unit for any reason, replacing the impeller at the same time is always worth it.
For the larger Mercury V6 Optimax 2.5L kit, see the Sierra 9252 Kit. For the Mercury V6 Optimax 3.0L kit, see the Sierra 9253 Kit. For Mercury 4-stroke outboard maintenance kits, see the Sierra 9243 Kit or Sierra 9244 Kit.
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.