Aftermarket Thermostat for Honda Marine 4-Stroke Outboards – Replaces 19300-ZW9-003 and 19300-ZY3-023
Aftermarket Thermostat for Honda Marine 4-Stroke Outboards – Replaces 19300-ZW9-003 and 19300-ZY3-023 is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
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Aftermarket Thermostat for Honda Marine 4-Stroke Outboards – Replac...
Aftermarket Thermostat for Honda Marine 4-Stroke Outboards – Replaces 19300-ZW9-003 and 19300-ZY3-023 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket thermostat is designed for selected Honda 4-stroke marine outboards. It regulates coolant flow to help maintain the engine's intended operating temperature and provides a replacement option for applications using Honda part numbers 19300-ZW9-003 or 19300-ZY3-023.
Before ordering, compare the part number, thermostat dimensions, seal arrangement, engine model, year, and serial-number range with your original component and the applicable Honda parts information. The broad horsepower range shown below is a product-reference range and does not replace application-specific verification.
- Aftermarket direct-replacement thermostat for selected Honda marine outboards.
- Corrosion-resistant stainless-steel and copper construction.
- Heat- and oil-resistant NBR rubber sealing material.
- Designed for installation in the thermostat housing.
Part Number Matrix
These are reference numbers associated with this replacement thermostat. Confirm the exact application before installation.
| Brand | Part Number |
|---|---|
| Honda | 19300-ZW9-003 |
| Honda | 19300-ZY3-023 |
| Honda | 19300ZY3023 |
| Honda | 19300ZW9003 |
| Sierra | 18-3628 |
| Sierra | 18-3541 |
Engine & Model Compatibility
The following Honda model references are associated with the stated replacement numbers. Model, year, stroke, shaft configuration, and serial-number conditions must be checked together; not every version within a model family is necessarily interchangeable.
| Brand | Model | Rated HP | Stroke | Listed Reference | Notes |
|---|---|---|---|---|---|
| Honda | BF8D / BFP8D | 8 | 4-Stroke | 19300-ZW9-003 | BFP8D Power Thrust version |
| Honda | BF9.9D / BFP9.9D | 9.9 | 4-Stroke | 19300-ZW9-003 | BFP9.9D Power Thrust version |
| Honda | BF15D / BFP15D | 15 | 4-Stroke | 19300-ZW9-003 | BFP15D Power Thrust version |
| Honda | BF20D / BFP20D | 20 | 4-Stroke | 19300-ZW9-003 | BFP20D Power Thrust version |
| Honda | BF25D | 25 | 4-Stroke | 19300-ZW9-003 | |
| Honda | BF30D | 30 | 4-Stroke | 19300-ZW9-003 | |
| Honda | BF40A / BF40D | 40 | 4-Stroke | 19300-ZW9-003 | |
| Honda | BF50A / BF50D | 50 | 4-Stroke | 19300-ZW9-003 | |
| Honda | BF60A / BFP60A | 60 | 4-Stroke | 19300-ZW9-003 | BFP60A Power Thrust version |
| Honda | BF75D | 75 | 4-Stroke | 19300-ZW9-003 or 19300-ZY3-023 | Verify the installed part number |
| Honda | BF90D | 90 | 4-Stroke | 19300-ZW9-003 or 19300-ZY3-023 | Verify the installed part number |
| Honda | BF200A | 200 | 4-Stroke | 19300-ZW9-003 or 19300-ZY3-023 | Verify the installed part number |
| Honda | BF225A | 225 | 4-Stroke | 19300-ZW9-003 or 19300-ZY3-023 | Verify the installed part number |
Technical Specifications
- Product Type
- Outboard engine thermostat
- Application
- Selected Honda marine 4-stroke outboards
- Installation Location
- Thermostat housing
- Fuel Type
- Gasoline
- Connection
- Direct-fit replacement where the listed reference applies
- Housing Material
- Stainless steel and copper
- Housing Color
- Metallic reddish-brown
- Dimensions
- Top gasket diameter: 27.0 mm; overall length: 33.6 mm
- Weight
- Approximately 0.03 kg (1.09 oz)
- Opening Temperature
- Approximately 60°C (140°F)
- Seal Material
- NBR rubber
- Warranty
- Subject to the applicable seller warranty and return policy
What's in the Box
- 1 x Thermostat
- 2 x Thermostat seals, listed as Honda reference 19302-921-003
Package contents are based on the product listing. Confirm the seal quantity and fit against the thermostat housing before installation.
Installation Notes
- Disconnect the battery and allow the engine to cool completely.
- Place a drain pan beneath the thermostat housing and follow the engine manufacturer's instructions for draining coolant, if required.
- Remove the bolts securing the thermostat housing cover.
- Remove the old thermostat and seal, noting their orientation.
- Clean the mating surfaces and remove old gasket material, deposits, and corrosion without damaging the housing.
- Install the replacement thermostat and seal in the correct orientation.
- Reinstall the housing cover and tighten the fasteners to the manufacturer's specified torque.
- Refill and bleed the cooling system using the recommended procedure and coolant.
- Reconnect the battery, start the engine, and check for leaks and proper cooling-system operation.
Use the service manual for the specific engine when handling coolant, torque values, bleeding procedures, and diagnostic checks.
Troubleshooting & FAQ
How do I know if my thermostat is failing?
Possible symptoms include overheating, an engine that takes unusually long to reach operating temperature, temperature fluctuations, warning alarms, or inconsistent cooling-system performance. Other cooling-system faults can produce similar symptoms, so diagnose the complete system before replacing the thermostat.
What is the opening temperature of this thermostat?
The listed opening temperature is approximately 60°C (140°F). Always compare this value with the specification for your exact engine model.
What is the purpose of the NBR rubber seal?
The NBR seal helps form a leak-resistant joint at the thermostat housing and is intended to withstand exposure to heat and engine fluids. Replace damaged or hardened seals rather than reusing them.
Is this part guaranteed to fit my Honda BF75D?
The BF75D is included in the listed reference applications, but fitment must still be confirmed using the engine's exact year, serial-number range, existing thermostat, and applicable OEM part number.
Is this an OEM part?
No. This listing is for an aftermarket replacement. Honda and Sierra numbers are provided only as manufacturer or aftermarket reference numbers for application comparison.
How should I verify compatibility?
Compare the existing part number, dimensions, seal arrangement, engine model, year, stroke, shaft configuration, and serial-number range. If any of these details differ, consult the engine service information before ordering.
What are the shipping and return terms?
Shipping availability, delivery times, warranty coverage, and return conditions depend on the seller's current policies and the destination. Review the terms shown at checkout or contact support before purchase.
Safety & Important Information
- Work only on a cool engine and follow the engine manufacturer's safety procedures.
- Verify the part number, dimensions, specifications, and package contents against your original part before installation.
- Do not operate the engine with a coolant leak or an improperly installed thermostat.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended when the correct procedure or engine-specific torque values are uncertain.
About Sea Sierra
- Pro-Grade Standards — We supply marine replacement parts selected for dependable performance in real-world operating conditions.
- Global Fulfillment — Shipping options and delivery estimates are provided according to destination and availability.
- Manufacturer-Direct Value — We aim to provide practical replacement solutions with clear application information.
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