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Description

Johnson/Evinrude Main Bearing Screw 0308752

The Johnson/Evinrude Main Bearing Screw set includes 4 bolts and is a powerhead fastener used on both standard OMC production outboards and the SST-45 / Formula Light racing engine.

On many production Johnson/Evinrude 2-cylinder engines, this screw is identified as a main bearing upper and lower screw.

The SST-45 factory parts catalog uses the same description and specifies 4 screws per powerhead.

What the 308752 Screw Does

The bolt is positioned around the upper and lower main bearing areas of the crankcase assembly.

Its job is to help clamp the crankcase and cylinder assembly securely around the main bearing locations.

Proper clamping in these areas helps maintain:

• Main bearing alignment
• Crankshaft positioning
• Crankcase sealing
• Correct internal clearances
• Stable powerhead assembly
• Consistent operation at higher RPM

Because these screws are located around critical crankshaft support areas, damaged or mismatched hardware should not be overlooked during a rebuild.

Stock Johnson/Evinrude Applications

Part number 308752 / 0308752 was used on a variety of standard Johnson/Evinrude outboards.

On later 2-cylinder production engines, it is commonly identified as:

“Screw, Main Bearing Upper & Lower”

OMC also used 308752 on older engine families where catalog descriptions may refer to it more generally as a crankcase-to-cylinder or lower crankcase screw.

This is common with OMC hardware, where the same fastener may appear under slightly different descriptions depending on engine family and production year.

SST-45 / Formula Light Application

For the SST-45 / Formula Light powerhead, the factory parts catalog specifies:

• Part Number: 308752
• Full OMC Number: 0308752
• Description: Screw, Main Bearing Upper & Lower
• Quantity Required: 4
• Location: Cylinder & Crankcase Assembly

These screws are separate from the other crankcase fasteners used on the SST-45 engine.

For comparison, the same assembly also uses:

• 308747 – Crankcase-to-Cylinder Screw – Quantity 2
• 308742 – Crankcase-to-Cylinder Screw – Quantity 8
• 308752 – Main Bearing Upper & Lower Screw – Quantity 4

Each fastener has its own designated location and should not be substituted simply because the screws may appear similar.

Common Reasons to Replace 308752 Bolts

Replacement should be considered when you find:

• Corroded threads
• Rounded or damaged heads
• Bent fasteners
• Pitting
• Damaged threads
• Evidence of over-tightening
• Mismatched hardware
• Fasteners that no longer tighten smoothly
• Unknown service history

Older outboards that have been operated in saltwater deserve especially careful inspection because corrosion can affect both the screw and the threaded crankcase hole.

Powerhead Rebuild Considerations

Whenever the crankcase is opened for service, inspect all four 308752 screws.

Before reassembly:

• Clean the threaded holes
• Inspect screw threads
• Check crankcase threads
• Clean all mating surfaces
• Verify main bearing position
• Confirm locating pins and internal components are correctly seated
• Follow the correct crankcase sealing procedure
• Install each fastener in its proper location
• Follow the specified tightening sequence and torque

Proper assembly around the main bearings is especially important because uneven clamping can affect crankshaft alignment and bearing support.

Why Correct Hardware Matters

Using a screw that is too long, too short, or otherwise incorrect can create problems such as:

• Incomplete clamping
• Bottoming in the threaded hole
• Damaged crankcase threads
• Misalignment
• Improper bearing support

For that reason, always match the OEM part number rather than substituting a bolt based only on diameter and thread pitch.

Key Features & Benefits

• Main Bearing Hardware – Used at the upper and lower main bearing areas
• Production OMC Application – Found on select standard Johnson/Evinrude outboards
• SST-45 / Formula Light Application – Factory-listed for the race powerhead
• Factory Quantity of 4 – Four used per SST-45 engine
• Important Rebuild Fastener – Helps maintain proper crankshaft and bearing support
• Replacement for Damaged Hardware – Ideal for corroded, rounded, or questionable original screws

Liquid Revolutions Racing Experience

At Liquid Revolutions, we separate the SST-45 crankcase hardware by part number and location during a rebuild rather than treating all of the crankcase screws as interchangeable.

The 308752 bolts are specifically used around the upper and lower main bearing areas, while 308742 and 308747 are used in other crankcase-to-cylinder positions.

Keeping the correct fastener in the correct location is a simple but important part of assembling a reliable SST-45 powerhead.

The same 308752 fastener is also used on standard Johnson/Evinrude production engines, making it relevant to both the recreational outboard owner and the Formula Light racer.