Mercruiser 18643A7 Engine Coupler Kit Genuine OEM Mercury-Mercruiser part. Replacement engine coupler kit for Mercruiser stern drives. Fits:MCM GM V6 & V8 (305 & 350 cid) engines (19831993) & 454 Mag Alpha Triangular shape, flywheel mount Special Order Item: This product is ordered specifically for your application. To help ensure proper fitment, please confirm compatibility with your engine model using our Parts Finder & Schematics Guide before placing your order. No returns or cancellations once processed.