Thermostat Kit – Fits Johnson Evinrude V4 Crossflow (Replaces 18-3673, 340975, 340976, 13270)

$20.99 $33.00

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Thermostat Kit – Fits Johnson Evinrude V4 Crossflow (Replaces 18-3673, 340975, 340976, 13270) is backordered and will ship as soon as it is back in stock.

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You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).

You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).

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Delivery and Shipping

Free standard shipping on all orders under 1 KG

If you have any questions, feel free to email us at info@sierramarines.com, and we’ll get back to you within 20–36 hours.

Product Details

This aftermarket Thermostat Kit – Fits Johnson Evinrude V4 Crossflow 2-Stroke engines, including 85 HP (1978–1980, 1993–1995), 88 HP (1984–1995), 90 HP (1983–1995), 100 HP (1979–1980, 1990–1995), 100 HP Commercial (1984–1989), 110 HP (1985–1989), 112 HP (1994–1995), 115 HP (1978–1995), 140 HP (1978–1985), 65 Jet (1994–1995), 80 Jet (1994–1995), and 90 Jet (1994) models.

It serves as a direct replacement for QuickMarine 5005440, HeuroFosh 18-3673, and Cylinman part numbers 18-3673, 340975, 340976, and 13270, among other cross-references.

Heavy-duty construction for reliable performance.
Includes precision seals designed to exceed original equipment specifications.
Comes as a complete kit for a full replacement.

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Brand	Part Number
QuickMarine	5005440
HeuroFosh	18-3673
Cylinman	18-3673
Cylinman	340975
Cylinman	340976
Cylinman	13270
JDLLONG	18-3673
Carbpro	18-3673

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For Johnson models, ensure your engine is a V4 Crossflow within the specified year range.

For Evinrude models, compatibility covers V4 Crossflow engines as listed.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.
Johnson	V4 Crossflow	65 Jet	2-Stroke	1994–1995	340975
Evinrude	V4 Crossflow	65 Jet	2-Stroke	1994–1995	340975
Johnson	V4 Crossflow	80 Jet	2-Stroke	1994–1995	340975
Evinrude	V4 Crossflow	80 Jet	2-Stroke	1994–1995	340975
Johnson	V4 Crossflow	85	2-Stroke	1978–1980, 1993–1995	340975
Evinrude	V4 Crossflow	85	2-Stroke	1978–1980, 1993–1995	340975
Johnson	V4 Crossflow	88	2-Stroke	1984–1995	340975
Evinrude	V4 Crossflow	88	2-Stroke	1984–1995	340975
Johnson	V4 Crossflow	90	2-Stroke	1983–1995	340975
Evinrude	V4 Crossflow	90	2-Stroke	1983–1995	340975
Johnson	V4 Crossflow	90 Jet	2-Stroke	1994	340975
Evinrude	V4 Crossflow	90 Jet	2-Stroke	1994	340975
Johnson	V4 Crossflow	100	2-Stroke	1979–1980, 1990–1995	340975
Evinrude	V4 Crossflow	100	2-Stroke	1979–1980, 1990–1995	340975
Johnson	V4 Crossflow	100 Commercial	2-Stroke	1984–1989	340975
Evinrude	V4 Crossflow	100 Commercial	2-Stroke	1984–1989	340975
Johnson	V4 Crossflow	110	2-Stroke	1985–1989	340975
Evinrude	V4 Crossflow	110	2-Stroke	1985–1989	340975
Johnson	V4 Crossflow	112	2-Stroke	1994–1995	340975
Evinrude	V4 Crossflow	112	2-Stroke	1994–1995	340975
Johnson	V4 Crossflow	115	2-Stroke	1978–1995	340975
Evinrude	V4 Crossflow	115	2-Stroke	1978–1995	340975
Johnson	V4 Crossflow	140	2-Stroke	1978–1985	340975
Evinrude	V4 Crossflow	140	2-Stroke	1978–1985	340975

Technical Specs

Product Type: Thermostat Kit
Dimensions: 7.5" x 6.0" x 1.0"
Weight: 0.23 kg (8.1 ounces)
Warranty: 3 Year Limited Warranty
Other Technical Attributes: Oil Fill Hub Cap; Heavy Duty; Precision Seals designed to exceed OE specifications.

What’s in the Box

2 x Thermostat (18-3673)
2 x Gasket (340975/340976)

Installation Notes

Allow the engine to cool completely and disconnect the battery terminals for safety.
Drain the engine coolant into a suitable container.
Locate and unbolt the thermostat housing cover.
Carefully remove the old thermostat, gasket, and seal, noting their orientation.
Thoroughly clean the mating surfaces of the thermostat housing and cover to ensure a proper seal.
Install the new thermostat from the kit, ensuring it is positioned in the correct direction.
Place the new gasket into position on the clean housing surface.
Reinstall the housing cover and tighten the bolts to the manufacturer-specified torque in a crisscross pattern.
Refill the cooling system with the manufacturer-recommended coolant.
Reconnect the battery, start the engine, and carefully check for any leaks around the housing as the engine warms up.
Monitor the temperature gauge to ensure the engine operates at the correct temperature.

Troubleshooting & FAQ

How do I know if this kit fits my specific engine model?

This kit is designed for Johnson and Evinrude V4 Crossflow engines. Please consult the 'Engine & Model Compatibility' table and verify your engine's HP and year range. It's crucial to match these details for a correct fit.

My engine is overheating. Could a faulty thermostat be the cause?

Yes, a stuck-closed thermostat is a common cause of engine overheating. Other signs include erratic temperature gauge readings or coolant leaks around the housing. This kit replaces the key components to resolve such issues.

When should the thermostat be replaced?

We recommend inspecting your thermostat during regular cooling system service (every 1-2 years) and replacing it if you notice corrosion, sticking, or if the engine fails to reach or maintain its proper operating temperature.

What is the difference between an OEM and aftermarket part?

This listing is an aftermarket replacement (not OEM). It's built to OEM-level specifications with comparable materials and manufactured in an ISO 9002 facility, where it is batch-inspected for consistency.

What are your shipping speed and costs?

We ship worldwide quickly—typical transit is 5–15 days. Standard shipping is free; expedited options appear at checkout where available.

What is the warranty and return policy?

This product is covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact our support team with your order details. Returns are accepted within our standard window for unused items in their original condition. See our policy page or reach out for instructions.

Safety & Important Info

Verify images and specifications against your original part before purchase. If anything differs—even if your model appears compatible—do not purchase.
This is an aftermarket replacement part, not an OEM component.
Professional installation is recommended for safety and optimal performance.

About Sea Sierra

Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
Manufacturer-Direct Value — Fair pricing without compromising on materials or quality control.

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