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Description

Johnson/Evinrude Cylinder to Crankcase Taper Pin 0305070

The Johnson/Evinrude Taper Pin is a locating pin used in the cylinder and crankcase assembly of many OMC outboard powerheads.

Its purpose is to accurately position the crankcase in relation to the cylinder block during assembly.

Taper Pin was used across a wide range of production Johnson/Evinrude engines and is also used in the SST-45 / Formula Light powerhead, making it relevant to both recreational outboard owners and racers rebuilding OMC-based engines.

What the Taper Pin Does

The cylinder block and crankcase must return to the correct position every time the powerhead is assembled.

The 305070 taper pin helps establish that alignment before the crankcase fasteners are tightened.

Proper positioning is important for maintaining:

• Crankshaft alignment
• Main bearing alignment
• Correct crankcase positioning
• Consistent mating-surface alignment
• Proper internal clearances
• Repeatable powerhead assembly

The bolts provide the clamping force, while the locating pins help ensure the two major castings are positioned correctly relative to one another.

Why a Taper Pin Is Used

Unlike a standard straight dowel, a taper pin gradually increases in diameter.

As the pin seats into its matching bore, the taper helps locate the mating components accurately and securely.

This design allows the crankcase and cylinder block to return to a repeatable position during assembly.

For a powerhead that may be disassembled multiple times during its life, maintaining these locating points is important.

Stock Johnson/Evinrude Applications

OMC used 305070 / 0305070 in the cylinder and crankcase assemblies of many production outboards.

Applications span multiple engine families and horsepower ranges, from smaller multi-cylinder engines through larger V4 and V6 OMC powerheads.

Depending on the engine, the parts catalog may describe it as:

• Taper Pin
• Pin, Taper
• Crankcase to Cylinder Pin
• Cylinder / Crankcase Locating Pin

The number of pins used varies by engine, so production-motor owners should confirm the required quantity from the parts diagram for their exact model.

SST-45 / Formula Light Application

The SST-45 / Formula Light engine also uses the 305070 taper pin as part of the cylinder and crankcase assembly.

On an SST-45 powerhead, accurate crankcase alignment is especially important because the engine regularly operates at sustained high RPM.

The taper pin works together with the crankcase fasteners and other locating components to ensure the crankcase returns to its intended position during a rebuild.

At Liquid Revolutions, we inspect the locating pins and their bores whenever an SST-45 powerhead is apart rather than assuming they are automatically reusable.

A damaged locating pin can affect how cleanly and consistently the crankcase goes back together.

Common Reasons to Replace 305070

Replacement should be considered when:

• Pin is missing
• Pin is bent
• Corrosion is present
• Surface is heavily pitted
• Pin has been damaged during disassembly
• Tapered surface is worn
• Pin no longer seats correctly
• Powerhead has previously been assembled with incorrect hardware
• Cylinder or crankcase assembly is being restored

Do not grind, reshape, or substitute a generic pin unless the dimensions and taper are known to match the original application.

Inspect the Locating Bore

The condition of the pin is only half of the equation.

During a powerhead rebuild, inspect the corresponding bore in the:

• Cylinder block
• Crankcase

Look for:

• Corrosion
• Elongation
• Burrs
• Impact damage
• Previous tool marks
• Debris preventing full seating

A new taper pin cannot properly locate the assembly if the bore itself is damaged.

Powerhead Assembly Tips

Before joining the crankcase and cylinder assembly:

• Clean the mating surfaces
• Inspect all locating pins
• Make sure each pin is fully seated
• Check the corresponding locating holes
• Verify main bearings are correctly positioned
• Confirm bearing dowels are properly engaged
• Apply the correct crankcase sealant
• Bring the crankcase halves together without forcing them
• Install fasteners in the correct locations
• Follow the proper tightening sequence and torque procedure

The crankcase should seat naturally over the locating components.

If excessive force is required, stop and determine what is preventing proper alignment.

Why Alignment Matters

Incorrect crankcase positioning can potentially affect:

• Main bearing support
• Crankshaft alignment
• Crankcase sealing
• Bearing fit
• Internal component clearance
• Powerhead durability

That makes a small component such as the 305070 taper pin much more important than its size might suggest.

Key Features & Benefits

• Cylinder-to-Crankcase Locating Pin – Helps accurately position major powerhead castings
• Tapered Design – Provides positive and repeatable alignment
• Production OMC Application – Used across numerous standard Johnson/Evinrude powerheads
• SST-45 / Formula Light Application – Used in the race powerhead cylinder and crankcase assembly
• Important During Rebuilds – Helps maintain proper alignment during powerhead reassembly
• Replacement for Damaged Originals – Ideal for corroded, worn, bent, or missing locating pins

Liquid Revolutions Racing Experience

At Liquid Revolutions, we pay close attention to the small locating components during an SST-45 powerhead rebuild because correct assembly depends on more than simply tightening the crankcase bolts.

The 305070 taper pin helps establish where the crankcase belongs before the fasteners provide the final clamping force.

On a race engine that may be disassembled repeatedly throughout its service life, keeping the locating pins in good condition helps make each rebuild more consistent.

The same principle applies to a stock Johnson/Evinrude engine: proper locating hardware helps the powerhead go back together the way OMC designed it.