Simpson #8 x 1-1/4" Flat Head Marine Screw in Type 316 Stainless Steel is engineered by Simpson Strong-Tie for boat building and marine trade applications where reliable fastening and maximum corrosion resistance are non-negotiable. Designed to fasten securely in fiberglass, plywood, and wood-substitute materials, this screw delivers long-lasting holding power in saltwater environments, chemically caustic conditions, and other demanding outdoor exposures. With a #2 Phillips flat head profile and high/low serrated threads, it is a go-to fastener for marine trim, rub rail, and molding installation on fiberglass boat hulls.

Key Features

• Type 316 Stainless Steel material and finish - provides the ultimate in corrosion protection, withstanding saltwater, harsh marine environments, and many chemically caustic conditions that would degrade standard fasteners
• High/Low Serrated Thread form with indentations ("teeth") - cuts easily and quickly through high-density materials like fiberglass and wood-substitute panels, reducing driving effort and cam-out risk during assembly
• Extra-sharp point type - speeds up screw starts during assembly, improving installation efficiency and reducing the chance of slipping on smooth surfaces like fiberglass
• #2 Phillips flat head drive - countersinks flush with the work surface for a clean, finished appearance on trim, rub rail, and molding applications
• 0.312 in. head diameter with 0.164 in. shank diameter - sized to provide strong clamping force without splitting or cracking the substrate material
• Screws over 1" long are threaded 2/3 of the shank length - the unthreaded shank section near the head pulls mating materials tightly together, creating a stronger mechanical joint
• Made for fiberglass, plywood, and wood-substitute materials - purpose-built thread geometry ensures reliable engagement across the material types most common in boat building and marine finishing work

Why This Product

• Purpose-built for marine environments - Type 316 stainless steel is specifically chosen for its superior resistance to saltwater and chemical exposure, making this screw the right choice where ordinary stainless or plated fasteners would corrode and fail over time
• Engineered thread design for high-density substrates - the high/low serrated thread form with serrated indentations was developed specifically for fiberglass and wood-substitute materials, meaning fewer stripped holes, faster drives, and more consistent holding strength compared to standard thread patterns
• Ideal for trim, rub rail, and molding on fiberglass boat hulls - the flat head profile sits flush at the surface, delivering a clean finished appearance on visible marine trim work without requiring additional countersinking tools
• Backed by Simpson Strong-Tie's marine fastener line - also available in a pan head version, giving installers the flexibility to select the right head style for each specific marine application without switching fastener brands

Specifications

• Brand: Simpson Strong-Tie
• Screw Size: #8
• Length: 1-1/4 in.
• Head Type: Flat Head
• Head Diameter: 0.312 in.
• Shank Diameter: 0.164 in.
• Drive Type: #2 Phillips
• Thread Type: High/Low Serrated Threads
• Point Type: Sharp Point
• Material: Type 316 Stainless Steel
• Finish: Type 316 Stainless Steel
• Country of Origin: Taiwan

Available Pack Options

• T08J125FX-RP15: 15 Pk
• T08J125FXC: 100 Pk
• T08J125FXM: 1000 Pk

Approved Applications

• Fastening trim, rub rail, and molding to fiberglass boat hulls
• Boat building and marine trade applications requiring superior corrosion protection
• Fastening into fiberglass, plywood, and wood-substitute materials in marine environments
• Applications exposed to severe marine conditions or many chemically caustic environments

Frequently Asked Questions

What makes Type 316 stainless steel different from standard stainless for marine use?

Type 316 stainless steel contains added molybdenum, which gives it superior resistance to saltwater, chlorides, and many chemically caustic substances compared to standard stainless grades. This makes it the preferred material for boat building, marine trim, and any fastening application exposed to ongoing moisture and corrosive conditions.

What materials can this screw fasten into?

This marine screw is designed to fasten securely in fiberglass, plywood, and wood-substitute materials. Its high/low serrated thread form - featuring indentations that act as teeth - cuts easily through high-density substrates, making it well suited for the types of composite and synthetic materials commonly used in marine construction.

How much of the shank is threaded on this 1-1/4" screw?

Screws more than 1" in length, including this 1-1/4" size, are threaded approximately 2/3 of the shank length. The unthreaded portion near the head allows the screw to draw mating materials tightly together for a stronger mechanical connection, which is important when securing trim, rub rail, or molding to a fiberglass hull.

Is this screw available in a different head style?

Yes. In addition to this flat head version, Simpson Strong-Tie's stainless steel marine screws are also available in a pan head style. The flat head is ideal when a flush, countersunk finish is needed on visible trim surfaces, while the pan head suits applications where a raised head profile is preferred.

Note: Product dimensions and/or thread length may differ from picture. Please see the item description above for specifications.