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Description

Johnson/Evinrude Screw Set 0308742

The Johnson/Evinrude Screw is a widely used OMC engine fastener found on both standard production outboards and SST-45 / Formula Light racing engines.

Depending on the engine model, 308742 may be used in several locations, including crankcase, cylinder, thermostat, cover, clamp, and related powerhead applications.

For the SST-45 powerhead, the factory parts catalog identifies 308742 specifically as the: “Screw, C’case to cyl.” and specifies 8 screws per engine.

Includes all 8 screws, making a complete replacement set for one SST-45 crankcase-to-cylinder assembly while still being useful for stock Johnson/Evinrude owners who need the same OEM fastener in another approved location.

Stock Johnson/Evinrude Applications

OMC used part number 308742 / 0308742 across a broad range of production Johnson/Evinrude engines.

Depending on the model, this screw may be used for:

• Crankcase-to-cylinder fastening
• Thermostat housings
• Engine covers
• Clamps
• Powerhead components
• Other engine hardware

Because OMC reused the same fastener in multiple locations, the exact quantity and purpose vary by engine.

SST-45 / Formula Light Application

On the SST-45 / Formula Light powerhead, 308742 is used to secure the crankcase to the cylinder assembly.

Factory quantity:

• Part Number: 308742 / 0308742
• Description: Screw, Crankcase to Cylinder
• Quantity Required: 8
• Application: SST-45 / Formula Light Powerhead

This includes the complete set of 8 screws required for one SST-45 engine.

Why These Screws Matter

Proper clamping between the crankcase and cylinder assembly is important for maintaining:

• Crankshaft alignment
• Bearing alignment
• Crankcase sealing
• Correct internal clearances
• Stable powerhead assembly
• Reliable engine operation

On a race engine, where the powerhead operates at sustained high RPM, consistent clamping becomes especially important.

Common Reasons to Replace

Replacement should be considered when the original hardware shows:

• Corroded threads
• Rounded or damaged heads
• Pitting
• Bent fasteners
• Damaged threads
• Evidence of previous over tightening
• Mismatched replacement hardware
• Fasteners that no longer thread smoothly

For older production engines, corrosion and repeated disassembly are common reasons these screws need replacement.

For SST-45 rebuilds, replacing all eight at once can help eliminate questionable or mismatched hardware.

Why Replace the Complete Set on an SST-45?

During a race-engine rebuild, the original screws may have been removed and installed many times over the years.

A complete matching set helps avoid:

• Mixed hardware
• Uneven thread condition
• Damaged fasteners
• Different head styles
• Unknown service history

Using all eight matching screws makes the final assembly cleaner and more consistent.

Installation & Service Tips

Before installation:

• Clean all threaded holes
• Inspect mating surfaces
• Check crankcase and cylinder threads
• Make sure locating pins are correctly positioned
• Use the correct crankcase sealing procedure
• Follow the proper tightening sequence
• Torque the fasteners to the correct engine specification

Do not use extra torque to compensate for damaged threads or warped mating surfaces.

Key Features & Benefits

• Used on Production OMC Engines – Found in multiple engine and powerhead locations
• SST-45 Crankcase Application – Factory-listed for crankcase-to-cylinder fastening
• Complete 8-Piece Set – Correct quantity for one SST-45 powerhead
• Ideal for Rebuilds – Useful during crankshaft, bearing, piston, or crankcase service
• Useful for Stock Motor Repairs – Same OEM fastener used on many standard Johnson/Evinrude applications
• Replaces Questionable Hardware – Good for corroded, rounded, damaged, or mismatched screws

Liquid Revolutions Racing Experience

At Liquid Revolutions, we use 308742 as part of the SST-45 crankcase assembly and prefer to replace hardware as a complete set during a rebuild.

For the racer, this 8-piece set gives you the full quantity required for one SST-45 powerhead.

For the stock Johnson/Evinrude owner, it is also a useful OEM-reference screw used in a variety of factory engine applications.

That makes 308742 a good example of a part shared between production OMC engines and the SST-45 racing platform.

For standard Johnson/Evinrude engines, verify the exact engine model and parts diagram because the same screw may be used in different locations and quantities.