My Account
Shopping Cart

Sierra 18-3408 Yamaha Outboard Water Pump Kit with Housing 2-Stroke

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

18-3408
09/12/2036 8:51 AM
Sale Price

$83.93

In Stock (10+)

delivery box

Usually delivered within 2 days

free shipping

FREE SHIPPING

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 18-3408 is a complete water pump replacement kit with housing designed for Yamaha 2-stroke outboard motors. Built to meet OEM specifications, this kit delivers everything needed to fully rebuild the cooling system water pump, helping prevent engine overheating and extending outboard life.

OEM Cross-Reference Numbers:

  • Yamaha 6H4-W0078-A00-00
  • Yamaha 6H4-W0078-00-00
  • Yamaha 6H4-W0078-01-00
  • Yamaha 6H4-W0078-A0-00
  • Yamaha 663-44311-02-00

Kit Includes:

  • Water Pump Housing
  • Impeller (18-3435)
  • Insert Cup (18-3297)
  • Impeller Key (18-0297)
  • Wear Plate (18-3436)
  • Water Pump Gasket (18-0294)
  • Water Pump Gasket (18-0256)
  • Water Pump Bolt (18-0292)
  • Oil Seal (18-99149)
  • Water Pump Bolt (18-3068)

Key Features:

  • Meets or exceeds OEM specifications for reliable fit and performance
  • Complete housing-included kit — no separate housing purchase required
  • Same core components as Sierra 18-3429, but includes the water pump housing
  • Designed for Yamaha 40 HP and 50 HP 2-stroke, 3-cylinder outboards (1984–1987)
  • Direct drop-in replacement — no modifications required

Regular water pump impeller replacement is essential preventive maintenance for any outboard engine. The Sierra 18-3408 kit simplifies the process by supplying all critical components in a single package, ensuring your Yamaha outboard's cooling system is fully restored to proper working order.

Products specifications

Description

Repair Kit w/ Housing

OEM Number

6H4-W0078-00, A0, 663-44311-02

So Far So good

Found exactly what I was looking for and for a good price. The checkout is nice and simple and easy to use. However, when I sent them an email before my order shipped saying that I need to have one item removed from the order, I never got an answer and my

Great service

Best product &amp; shipping prices found! Thanks! We look forward to doing more business with Autoplicity.

Easy site to work with, good representation of products.Extremely fair prices.

Had the absolute best price for a bike carrier. Quick shipping, lots of email feedback so you know what's happening to your order. Highly recommended! AAAAA++++++++++++

Very fast shipping, always great prices.

I'm always had a great experience!

Fast and easy. Good prices

Excellent price on kirkey seats! I will be buying from them again. Thanks for the prompt service

Fast Shiping Good Services Verry Good Pricing

The lowest price on the internet for this part and they shipped it fast!!!! This was definitely a very good experience!<br>I will gladly buy parts from this company again!

Wow super fast shipping and I ordered over a holiday weekend. Will be doing business with this site again soon.

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