Piston Assembly (Starboard Side) – Fits Mercury/Mariner 135-200 HP V6 Outboards (Replaces 785-9738T9)

$155.30 $248.00

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Piston Assembly (Starboard Side) – Fits Mercury/Mariner 135-200 HP V6 Outboards (Replaces 785-9738T9) is backordered and will ship as soon as it is back in stock.

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Product Details

This aftermarket Piston Assembly (Starboard Side) is designed for Mercury/Mariner 2.5L V6 outboards (135–200 HP) from 1991–2000. It fits a wide range of models, including the XR2, XR6, MAG III, V-140, V-175, and V-200 series.

It serves as a direct replacement for Mercury OEM part numbers 785-9738T9 and 9738T9.

Installs in the starboard side of the engine block.
Made from a durable, high-grade aluminum alloy.
Features a standard size (Ø 3.50") loop-charged piston design for optimal performance.

Part Number Matrix

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

Brand	Part Number
Mercury	785-9738T9
Mercury	9738T9

Engine & Model Compatibility

Confirm your engine model/year in the table below.

This part is designed for specific Mercury and Mariner V6 outboard engines manufactured between 1991 and 2000. Always verify your engine's serial number against the ranges provided.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Mercury	140 JET	140	2-Stroke	1991–1999	785-9738T9	Serial Range: 0G960500-0T178499
Mercury	XR-6	150-200	2-Stroke	1991–2000	785-9738T9	Serial Range: 0G960500-1B226999
Mercury	MAGNUM III	150-200	2-Stroke	1991–2000	785-9738T9	Serial Range: 0G960500-1B226999
Mercury	V-135	135	2-Stroke	1991–1999	785-9738T9	Serial Range: 0G960500-0T178499
Mercury	V-140 (International)	140	2-Stroke	1999–2000	785-9738T9	Serial Range: 0T178500-1B226999
Mercury	V-150	150	2-Stroke	1991–2000	785-9738T9	Serial Range: 0G960500-1B226999
Mercury	V-150 (EFI)	150	2-Stroke	1991–1999	785-9738T9	Serial Range: 0G960500-0T408999
Mercury	V-175 (EFI)	175	2-Stroke	1991–1999	785-9738T9	Serial Range: 0G960500-0T408999
Mercury	V-200	200	2-Stroke	1991–2000	785-9738T9	Serial Range: 0G960500-1B226999
Mercury	V-200 (EFI)	200	2-Stroke	1991–1999	785-9738T9	Serial Range: 0G960500-0T408999
Mercury	200 EFI PRO MAX/SUPER MAG	200	2-Stroke	1991	785-9738T9	Serial Range: 0G857000-0G858150
Mercury	175XR2 JET DRIVE	175	2-Stroke	1991–1999	785-9738T9	Serial Range: 0E369300-0E433153
Mercury	210 CARB JET DRIVE	210	2-Stroke	1991–1999	785-9738T9	Serial Range: 0E384500-0E433153
Mercury	210 CARB M2 JET DRIVE	210	2-Stroke	1991–1999	785-9738T9	Serial Range: 0E373939-0E426999

Technical Specs

Product Type: Piston Assembly (Starboard Side)
Installation: Engine Block, Starboard Side
Fuel Type: Gasoline
Housing Material: Aluminum Alloy
Dimensions: 16.5" × 9.0" × 9.0"
Weight: 0.65 kg (1.44 lbs)
Other Technical Attributes: Standard Size (Ø 3.50"), Loop-charged Piston

What’s in the Box

1 x Piston Assembly (785-9738T9)
1 x Piston Rings (included in assembly)
1 x Wrist Pin (included in assembly)

Installation Notes

Disconnect the battery and drain all engine fluids (coolant and oil).
Remove the cylinder head and any components blocking access to the piston.
Carefully rotate the crankshaft to expose the connecting rod bolts for the target piston.
Remove the connecting rod cap and gently push the old piston assembly out of the cylinder.
Clean the cylinder bore and inspect for any damage or wear. Honing is recommended.
Lubricate the new piston, rings, and cylinder wall with engine assembly lube.
Use a ring compressor to carefully install the new piston assembly into the cylinder, ensuring correct orientation.
Re-attach the connecting rod cap and torque its bolts to the manufacturer's specified values.
Reinstall the cylinder head with a new gasket and reassemble all other components.
Refill engine fluids, reconnect the battery, and follow the engine's break-in procedure before full-throttle operation.

Troubleshooting & FAQ

How do I know if this piston fits my engine?

The best way to confirm fitment is to check your original part number against the cross-references listed in our Part Number Matrix. Additionally, verify your engine's model, horsepower, and serial number fall within the ranges specified in the Engine & Model Compatibility table.

Is this piston for the port or starboard side?

This specific assembly is for the starboard (right) side of the engine block. Mercury V6 engines use different pistons for the port and starboard sides due to the loop-charged design. Ensure you are ordering the correct side for your needs.

What are the signs of a failing piston?

Common symptoms include loss of compression in a cylinder, excessive smoke from the exhaust, a knocking or rattling sound from the engine, and metal shavings in the engine oil. A professional diagnostic is recommended to confirm the cause.

Does this kit include the piston rings and wrist pin?

Yes, this is a complete piston assembly. It comes with the piston rings and wrist pin pre-installed and ready for installation.

What is the proper break-in procedure for a new piston?

Follow the guidelines in your engine's service manual. Generally, this involves running the engine at varied, low-to-mid RPMs for several hours without sustained full-throttle operation to allow the new rings to seat properly against the cylinder wall.

OEM vs. Aftermarket?

This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.

Shipping speed & cost?

We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.

Warranty & returns?

Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.

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

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