Piston Kit – Fits Mercury/Mariner/Force 35-150 HP Crossflow Engines (Replaces 774-9137A11)

Product Details

This aftermarket Piston Kit – Fits Mercury/Mariner/Force 35-150 HP Crossflow Engines (Replaces 774-9137A11) is designed for Mercury/Mariner/Force 35–150 HP 2-Stroke engines with a 2.875" bore, specifically for crossflow models from 1970–1990. This is a .030 oversize piston, intended for cylinders that have been machined during an engine rebuild.

It serves as a direct interchange for several OEM and aftermarket part numbers, including Mercury/Mariner 774-9137A11/774-9137A14, Sierra 18-4530/18-4156, Mallory 9-53224, GLM 14050, and RAREELECTRICAL 100-15-06K.

• This is an internal engine component requiring professional installation.
• The low dome piston design includes a power port hole and can replace original high dome pistons without affecting engine operation.
• The complete kit includes the piston, keystone-style rings, wrist pin, and retainers.

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For Mercury/Mariner/Force engines, you must verify your engine's serial number against the listed ranges to ensure an exact match, as specifications can vary by manufacturing location (USA, BEL, CAN, AUS).

Technical Specs

Product Type

Piston Kit (.030 oversize)

Installation

Internal engine component

Piston Design

Low dome with power port hole

Bore Size

2.875" + .030 = 2.905" (73.8mm)

Deflector Height

.650"

Ring Type

Keystone

Application

Crossflow 2, 3, 4 & 6-cylinder inline direct charge engines

Original Bore Size

2.875" (73mm)

Other Technical Attributes

Can replace high dome pistons without affecting engine operation

Box Dimensions

15.5" L x 12.0" W x 12.0" H

What’s in the Box

• 1 x Piston (.030 Oversize)
• 1 x Set of Keystone Piston Rings
• 1 x Wrist Pin
• 2 x Retainers

Installation Notes

1. Thoroughly clean the cylinder and inspect for any damage or warping before installation.
2. Confirm the cylinder has been machined to match the new piston's 2.905" diameter.
3. Install the keystone-style piston rings onto the piston, ensuring they are oriented correctly per your engine's service manual.
4. Lubricate the piston, rings, and cylinder wall with fresh 2-stroke engine oil.
5. Use a ring compressor tool to gently install the piston and connecting rod assembly into the cylinder.
6. Ensure all components (rod caps, bolts) are torqued to the manufacturer's exact specifications. Always consult your OEM service manual for precise procedures.

Troubleshooting & FAQ

Safety & Important Info

• Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
• This is an aftermarket replacement, not an OEM component.
• Professional installation is recommended for safety and performance.

About Sea Sierra

• Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
• Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
• Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.