MERCRUISER STERNDRIVE / INBOARD APPLICATIONS:
UNIVERSAL FIT — MERCRUISER WITH 4" EXHAUST OUTLET:
• MerCruiser Alpha One Sterndrive (4" exhaust outlet)
• MerCruiser Alpha One Gen II Sterndrive (4" exhaust outlet)
• MerCruiser Bravo One Sterndrive (4" exhaust outlet)
• MerCruiser Bravo Two Sterndrive (4" exhaust outlet)
• MerCruiser Bravo Three Sterndrive (4" exhaust outlet)
• MerCruiser MC-I / R-MR Sterndrive (legacy 4" applications)
• MerCruiser inboard installations with 4" exhaust outlet
ENGINE COMPATIBILITY:
• MerCruiser 4.3L V6 (262 CID) 1985-Present
• MerCruiser 5.0L V8 (305 CID) 1985-Present
• MerCruiser 5.7L V8 (350 CID) 1985-Present
• MerCruiser 7.4L V8 (454 CID) 1988-Present
• MerCruiser 8.2L V8 (502 CID) Performance applications
• Most MerCruiser V6/V8 engines with 4-inch transom exhaust outlet
• Production years: 1994 and Up
• NOTE: Fitment determined by exhaust diameter, not engine type
PRODUCT SPECIFICATIONS:
• Type: External Exhaust Flapper / Protector Valve
• Size: 4 INCH (101.6mm) diameter ONLY
• Material: EPDM Rubber with UV Stabilizer
• Construction: One-piece molded rubber flap
• Hardware: Stainless Steel Hose Clamp (included)
• Position: External transom exhaust outlet
• Function: Prevents water backflow into exhaust system
• Salt/Fresh Water: Compatible with both environments
• Resistance: UV, ozone, heat, weather aging
• Condition: New
WHAT THIS FLAPPER DOES:
• Prevents backflow of water into exhaust system
• Critical when boat comes off plane or slows
• Essential in following seas / rough water conditions
• Protects engine from hydraulic lock damage
• Reduces risk of water entering exhaust valves
• Maintains proper exhaust gas flow direction
INSTALLATION PROCEDURE (3 STEPS):
• Step 1: Slide flapper over 4" exhaust pipe at transom
• Step 2: Position flap to open downward (gravity assist)
• Step 3: Tighten included stainless steel hose clamp
• Tools required: Screwdriver only
• Installation time: Under 5 minutes per flapper
• DIY-friendly with no special tools
OEM SUPERSESSION CHAIN:
• Original OEM: 12644A1 (older Mercury format)
• Current OEM: 12644Q01 (newer Quicksilver Q-prefix)
• Both numbers reference same physical product
• Supersession reflects Mercury catalog system update
SIZE FAMILY (different products for different outlets):
• 3 inch exhaust flappers (separate listing)
• 4 INCH exhaust flapper (THIS LISTING)
• 5"+6" exhaust flappers (separate listing)
• ALWAYS verify your exhaust diameter before ordering
OEM PART NUMBERS:
• Mercury/Quicksilver: 12644A1 (original)
• Mercury/Quicksilver: 12644Q01 (current supersession)
• MPN: 18-4457
WHEN TO REPLACE:
• Annual inspection recommended
• Replace if rubber shows cracking or hardening
• Replace if flap doesn't seal flat against opening
• Replace if hose clamp shows corrosion
• Replace immediately after storm or saltwater damage
• Replace as part of regular winterization service
CRITICAL FITMENT WARNINGS:
• 4 INCH exhaust outlet ONLY - measure before ordering
• Does NOT fit 3 inch or 5"+6" exhaust outlets (different products)
• Does NOT fit Mercury outboard motors (this is sterndrive/inboard)
• Does NOT fit Volvo Penta or OMC Cobra sterndrives
• Externally mounted (NOT internal Y-pipe water shutter — that's different)
• Easy DIY installation - no special tools required
SHIPPING TIME: Orders placed and paid by 4:00 PM EST will ship the same business day (excluding weekends and holidays which will ship next business day). Tracking information will be sent via e-mail by our shipping department. Delivery times can vary by location and shipping method. Typically, free shipping to the eastern US is estimated to be delivered in 1-2 business days, where deliveries to the western US (or most remote locations) may take up to 4-6 business days.
Items purchased with FREE SHIPPING & FLAT SHIPPING RATES only apply to US 48 CONTIGUOUS STATES and does NOT include APO/FPO/MPO (these areas are subject to a shipping surcharge). International Shipping, US Non-Continental shipping - which includes Alaska, Hawaii, Puerto Rico, US Territories and APO/FPO/MPO - all have 3-10 business day delivery times. Shipments will be delivered by UPS, FEDEX, or USPS and the carrier will be selected at our discretion.
We also offer Expedited Shipping WORLDWIDE, including Saturday delivery (Saturday Delivery is an extra $15.00 and is not always available).
SHIPPING RATES: Please add your items to a cart to determine your shipping costs and rates. Please note that international orders may be subject to customs and duty fees; all international shipping costs are the responsibility of the customer.
CANCELLING ORDERS: In the event you need to cancel or change your order you may do so within 24 hours, provided your order has not been shipped, by contacting us through eBay's messaging center. Please make sure the Ship-To address you use during checkout is correct. All orders that are returned to sender or undeliverable are subject to a 20% Return Charge.
RAREELECTRICAL products, when properly installed, are warranted against defects in materials and workmanship to the original purchaser for a period of one (1) year from the date of purchase. Warranty does not cover failure due to accident, abuse, neglect or as the result of normal wear and
