{"product_id":"merc-170","title":"Mercury MerCruiser Stainless Steel Washer 12-34931 | 0.406\" x 0.734\" x 0.063\"","description":"\u003ch2\u003eMercury MerCruiser Stainless Steel Washer — Part No. 12-34931\u003c\/h2\u003e\n\u003cp\u003eThis is the genuine Mercury Marine OEM stainless steel washer listed under part number \u003cstrong\u003e12-34931\u003c\/strong\u003e (base number \u003cstrong\u003e34931\u003c\/strong\u003e). A precision-dimensioned flat washer in marine-grade stainless steel, it is used where the Mercury or MerCruiser parts diagram specifically calls for this number — providing the correct bearing surface, load distribution, and corrosion resistance for the assembly location. When the diagram calls for 12-34931, a generic hardware-store washer is not an equivalent substitute.\u003c\/p\u003e\n\n\u003ch2\u003ePart Details\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e 12-34931\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBase Number:\u003c\/strong\u003e 34931\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eType:\u003c\/strong\u003e Flat Washer — Stainless Steel\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eInside Diameter (ID):\u003c\/strong\u003e 0.406 in.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOutside Diameter (OD):\u003c\/strong\u003e 0.734 in.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThickness:\u003c\/strong\u003e 0.063 in.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMaterial:\u003c\/strong\u003e Stainless steel (marine-grade corrosion resistance)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eType:\u003c\/strong\u003e Genuine Mercury Marine OEM washer\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eCompatible Applications\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eUse where the Mercury, MerCruiser, or Quicksilver parts diagram specifically calls for part number 12-34931 or 34931\u003c\/li\u003e\n\u003cli\u003eConfirm fitment by engine or drive serial number, assembly location, and current Mercury parts diagram before ordering\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cem\u003eWasher fitment must be confirmed by part number and diagram position. Similar washers vary in inside diameter, outside diameter, thickness, and material — do not substitute by size alone.\u003c\/em\u003e\u003c\/p\u003e\n\n\u003ch2\u003eAlternate \u0026amp; Superseded Part Numbers\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e12-34931\u003c\/strong\u003e — current Mercury\/MerCruiser formatted number\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e34931\u003c\/strong\u003e — base part number\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhen to Replace\u003c\/h2\u003e\n\u003cp\u003eReplace this washer if it is corroded, deformed, cracked, missing, or no longer providing a flat bearing surface. Also replace any time the fastener assembly it belongs to is disassembled for service — especially in saltwater or high-vibration environments where washers can corrode or fatigue over time.\u003c\/p\u003e\n\n\u003ch2\u003eInstallation Tips\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eConfirm the washer is installed in the correct orientation and position as shown in the Mercury parts diagram\u003c\/li\u003e\n\u003cli\u003eInspect the mating surface and fastener threads for corrosion or damage before reassembly\u003c\/li\u003e\n\u003cli\u003eFollow the Mercury service manual torque specification for the specific assembly location\u003c\/li\u003e\n\u003cli\u003eDo not substitute a washer of a different thickness — the 0.063\" thickness is part of the designed fastener stack-up at this location\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eTechnical FAQ\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eQ: Can I use a standard hardware-store stainless washer of the same size?\u003c\/strong\u003e\u003cbr\u003eA: Not recommended for diagram-specified locations. OEM marine washers are dimensioned and graded for the specific fastener stack-up and clamping requirements of the assembly. A hardware-store washer may differ in thickness tolerance, material grade, or surface finish in ways that affect the joint.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: How do I find where this washer is used on my engine or drive?\u003c\/strong\u003e\u003cbr\u003eA: Look up your engine or drive serial number in the Mercury parts diagram and confirm the diagram calls for 12-34931 at the specific assembly location you are servicing. If you’re unsure, our parts team can help verify before you order.\u003c\/p\u003e\n\n\u003ch2\u003eParts Desk Insights\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eBest use case:\u003c\/strong\u003e This washer is the right call when the parts diagram specifically calls for 12-34931 and an OEM-dimensioned stainless replacement is needed. Its stainless steel construction makes it well-suited to the corrosive marine environment, and the precise 0.406\" ID \/ 0.734\" OD \/ 0.063\" thickness means it fits the designed fastener stack-up correctly. It’s a low-cost part that’s easy to overlook and worth ordering ahead of any service that involves disassembling the assembly it belongs to.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCommon issues:\u003c\/strong\u003e The most frequent problem is substituting a generic washer by approximate size, then discovering the thickness or OD doesn’t match the original stack-up. Even small dimensional differences can affect how the fastener clamps the assembly. Always order by part number from the diagram. The second common issue is not replacing corroded or deformed washers during service — a washer that looks serviceable may have lost its flatness or surface integrity after years in a marine environment.\u003c\/p\u003e","brand":"MERC","offers":[{"title":"Default Title","offer_id":43563854430244,"sku":"34931","price":3.89,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0743\/5799\/7604\/files\/730019f3-a102-4a8d-a935-fea7d7709cc4.png?v=1787266847","url":"https:\/\/marisolmarine.com\/products\/merc-170","provider":"Marisol Marine Company","version":"1.0","type":"link"}