HGE — Open Riser Gasket MerCruiser V6 V8 — HGE-43781
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The HGE Marine Engine Products 43781 Open Riser Gasket is an aftermarket marine exhaust gasket used between the exhaust manifold and the upper riser or elbow on compatible MerCruiser V6 and V8 center-rise exhaust systems. The open-flow gasket profile allows unrestricted water-jacket transfer between the manifold and riser, making it intended for raw-water-cooled exhaust configurations where cooling water must circulate freely through the manifold and riser assembly.
Key Features
- Product code: HGE-43781
- Part number: 43781
- Gasket type: Open riser / open-flow exhaust gasket
- Application location: Between exhaust manifold and riser/elbow
- Cooling passage design: Fully open coolant transfer passages
- Bolt pattern: Standard 4-bolt MerCruiser-style center-rise footprint
- Application type: Raw-water-cooled MerCruiser V6 and V8 exhaust systems
- Construction: Marine exhaust gasket material designed for high heat, water exposure, and exhaust service
Engine Compatibility
This gasket is intended for compatible MerCruiser V6 and V8 marine engines using the open-style manifold-to-riser gasket configuration, including applications commonly found on:
- MerCruiser V6: 4.3L, 4.3LH, and 4.3L EFI packages
- MerCruiser V8: 5.0L, 5.7L / 350 MAG, 6.2L, and 7.4L / 454 CID engines
- Exhaust configuration: Classic MerCruiser center-rise manifold and riser/elbow assemblies using the matching 4-bolt open gasket footprint
Use this gasket only where the engine’s exhaust diagram, cooling layout, or existing gasket confirms an open water-passage design.
Fitment Notice
The open gasket design is not interchangeable with restricted or block-off riser gaskets. Engines with closed freshwater cooling, heat exchanger systems, or riser-only raw-water flow may require a restricted or block-off gasket instead. Installing an open gasket where a restricted or blocked cooling passage is required can cause incorrect water routing, overheating, or exhaust system damage.
Always verify the engine serial number, cooling system type, exhaust manifold style, riser/elbow casting, and original gasket passage layout before installation.
When This Part Needs Replacement
Replace the riser gasket whenever the riser, elbow, or exhaust manifold is removed. The gasket should also be replaced if there are signs of water leakage, exhaust soot tracking, saltwater staining, rust trails, overheating, steam, water intrusion risk, or corrosion around the manifold-to-riser joint.
A used exhaust riser gasket should not be reused, as compression set, heat cycling, and saltwater exposure can prevent it from sealing correctly after disassembly.
Installation Notes
Clean both mating surfaces thoroughly before installation and check the manifold and riser for corrosion, pitting, warping, blocked water passages, or internal rust scale. Confirm the new gasket matches the old gasket’s water-passage layout before bolting the riser back in place.
Use the correct marine exhaust fasteners and follow the MerCruiser service procedure for bolt tightening sequence and torque. Inspect riser bolts, mounting threads, exhaust shutters, hoses, clamps, and adjacent gaskets during the same service, especially on saltwater engines or older exhaust assemblies.
Alternate/Cross-Reference Part Numbers
- HGE: 43781
- Marisol / product code: HGE-43781
- Mercury Marine / Quicksilver: 27-863726
- Mercury Marine / Quicksilver: 27-39915
- Sierra Marine: 18-2840-1
- GLM Marine: 30240
- Mallory Marine: 9-29101
Parts Desk Insight
The important detail on this gasket is the open coolant-passage layout. Similar MerCruiser riser gaskets can share the same outside shape and bolt pattern but route water differently. Match the gasket style to the engine’s cooling system and original exhaust configuration before ordering, especially when servicing closed-cooled engines or mixed manifold/riser setups.
Shipping: Ships same or next day for fast Canada wide shipping. ⚓
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
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