My Account
Shopping Cart

Sierra 18-9078 Stainless Steel Water Pump Plate Washer for Outboard Engines

Manufacturer

Sierra

<h3>Sierra: Six Decades of Marine Aftermarket Excellence</h3><p><strong>Sierra</strong> has spent nearly 60 years earning its reputation as one of the most trusted names in the marine aftermarket industry. Originally focused on engine and drive components for boats, the brand has grown into a comprehensive source for nearly everything a boater needs to keep their vessel running at its best — from precision instrumentation to complete engine rebuild hardware.</p><p>Now operating as a brand of Dometic, Sierra manages global aftermarket distribution from a 300,000 sq. ft. facility in Litchfield, Illinois. The Sierra brand today encompasses not only its flagship marine parts line but also well-established marine names like Shields and Moeller, offering boaters a broader catalog than ever before. Whether you own an outboard, inboard, or sterndrive, Sierra's engineering team designs products to meet or exceed OEM specifications.</p><h3>Precision Instrumentation You Can Trust on the Water</h3><p>One of Sierra's most recognized product areas is its marine instrumentation lineup. The brand's <a href="/7570-sierra-gauge-set-1480">gauge sets</a> cover everything from classic analog instrument clusters to advanced digital multi-function displays. Sierra offers packages suited to outboards, sterndrives, and gasoline-powered inboards, with options ranging from coordinated analog kits in styles like Arctic, Eclipse, and Amega to modern touchscreen solutions like the R3 multi-function gauge. Features such as scratch-resistant domed glass lenses, silicone-dampened pointers, and perimeter backlighting make these instruments highly readable in all conditions.</p><p>Behind every accurate gauge reading is a properly calibrated sending circuit. Sierra's <a href="/7570-sierra-gauge-resistor-47908">gauge resistors</a> are a critical part of that chain, ensuring the signals from sensors and sending units are correctly interpreted by your instruments. These components are built to marine-grade standards to resist moisture, vibration, and corrosion — the realities of life on the water.</p><h3>Engine Internals Built to OEM Standards</h3><p>Sierra's history in marine power is perhaps best demonstrated by its deep catalog of engine components. The brand's <a href="/7570-sierra-engine-gasket-set-5404">engine gasket sets</a> cover a wide range of outboard and inboard applications and are engineered to deliver reliable seals in the demanding thermal and chemical environment of a marine engine. For boaters performing seasonal overhauls, top-end rebuilds, or full engine restorations, Sierra gasket kits are a go-to resource trusted by professional marine technicians and DIY boaters alike.</p><h3>A Complete Marine Parts Partner</h3><p>Beyond instrumentation and engine internals, Sierra's catalog spans fuel systems, electrical supplies, steering components, shore power, and more — all covered by what the brand calls an industry-leading warranty. Sierra also maintains a comprehensive parts-finder tool that enables cross-referencing with OEM part numbers from major manufacturers including Mercury, Yamaha, Suzuki, Volvo Penta, and others, making it straightforward to find the right replacement part for virtually any application.</p>

Part Number

18-9078
09/12/2036 6:27 AM
Sale Price

$3.61

In Stock (10+)

delivery box

Usually delivered within 2 days

Authorize Seller Badge
No Hassle Returns

No Hassle Returns

Live-in-stock inventory

Live-in-stock inventory

Fitment guaranteed

Fitment guaranteed

Product Details

The Sierra 18-9078 is a stainless steel water pump housing plate washer designed as a direct replacement for Yamaha outboard engines and select Mercury Marine applications. This washer seats on the driveshaft directly above the impeller and helps secure the impeller down against the water pump plate, ensuring proper cooling system operation.

Constructed from corrosion-resistant stainless steel, this washer is built to withstand the harsh marine environment and provides a durable, long-lasting alternative to the OEM part at a competitive price point.

Key Features:

  • Material: Stainless steel construction for superior corrosion resistance
  • Function: Water pump housing plate washer — holds the impeller firmly against the water pump plate
  • Direct Replacement: Drop-in fit for Yamaha OEM part number 90201-22M01-00
  • Cross-Reference: Replaces Mallory 9-43713 and Mercury Marine 12-8556822

OEM Cross-Reference Numbers:

  • Yamaha: 90201-22M01-00
  • Mercury Marine: 12-8556822
  • Mallory: 9-43713
  • Sierra: 18-9078

I had a great first time experiance with Autoplicity. My K&N Filter came on time just as promised and saved me about $40 over my local Autozone including shipping! I will be back

I finally had time to install my part. The steering wheel hub was exactly what I needed at a great price and delivered promptly. Thanks for the great service.

Super pricing, fast shipments, good selection they have it all.

Great product, fast shipping and cheap price. Would buy from again, Thanks!

Quick and easy

Awesome and quick ship time. Very informative with the ship date<br> Will be doing business with them again

Made a hard to find part easy.When I received the part it looked like a return from the tape job on the box. Part looked new but handled in an attempted install way of appearance. I'm sure it'll be fine.

Only site i could find what i was looking for and at an unbeatable price. Shipping was very fast, no problems what so ever. Would recommend this site to anybody and everybody! Will be shopping here again real soon!!!

no body answers the phone

1st time buyer

theyerr grrreeeeaaa T

shopping was quick and easy!

received a follow up phone call within a hour letting me know that my order #5153 would be coming from a certian warehouse and about what time it will arrive...Great service!!!highly recommend

Share icon
Return Policy
Returns are easy at Boatplicity

Not happy with a purchase? No problem. We've made returning items as easy as possible. And most purchases can be returned for free for 30 days. Learn more about our Returns Policy