Gasket – Mercury Marine 105-225 HP Outboards (Replaces 27-67074, 27-88727, 27-99173, 27-991731, 27-991732, 27-991734)

$17.06 $27.00

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Gasket – Mercury Marine 105-225 HP Outboards (Replaces 27-67074, 27-88727, 27-99173, 27-991731, 27-991732, 27-991734) is backordered and will ship as soon as it is back in stock.

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Free standard shipping on all orders under 1 KG

If you have any questions, feel free to email us at info@sierramarines.com, and we’ll get back to you within 20–36 hours.

Product Details

This drive housing gasket is a direct-fit replacement for Mercury Marine 2-stroke outboard engines ranging from 105 HP to 225 HP, covering model years from approximately 1978 to 2016. It ensures a proper seal between the drive shaft housing and the exhaust plate, which is critical for preventing water and exhaust leaks.

It serves as a direct interchange for Mercury-Mercruiser part numbers 27-991734, 27-991732, 27-991731, 27-99173, 27-88727, and 27-67074, as well as aftermarket equivalents like Sierra 18-2511-9.

Installs between the drive housing and exhaust plate.
Engineered to meet or exceed original equipment specifications.
Provides a reliable seal against exhaust and water intrusion.

Part Number Matrix

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

Brand	Part Number
Mercury-Mercruiser	27-991734
Mercury-Mercruiser	27-991732
Mercury-Mercruiser	27-991731
Mercury-Mercruiser	27-99173
Mercury-Mercruiser	27-88727
Mercury-Mercruiser	27-67074
Sierra	18-2511-9
PARTSDEPOT	27-991734
Buckshot Racing	991734

Engine & Model Compatibility

Confirm your engine model and serial number range in the table below to ensure accurate fitment.

For Mercury engines, compatibility is defined by specific model names and serial number ranges. Please check your engine's identification plate carefully.

For Mariner engines, this part fits a broad range of 105 HP to 225 HP models from 1978–2005. Check specific notes for bore size details.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Mercury	MAGNUM III	N/A	N/A	0G960500–1B226999	27-991734	Also confirmed for 0G303046–0G760299, 0G760300–0G960499, 0D082000–0G303045
Mercury	V-115 DFI	115	2-Stroke	0G960500–0T178499	27-991734
Mercury	V-135	135	N/A	0G960500–0T178499	27-991734	Also confirmed for 0G303046–0G760299, 0G760300–0G960499, 0D082000–0G303045
Mercury	V-135 DFI (2.5L)	135	2-Stroke	0G960500–1B417702 & Up	27-991734	Covers various serial ranges including 0T178500–0T800999, 0T801000–1B226999, 1B227000–1B417701
Mercury	V-140 (INTERNATIONAL)	140	N/A	0T178500–1B226999	27-991734
Mercury	V-150	150	N/A	0G960500–1B226999	27-991734	Also confirmed for 0G303046–0G760299, 0G760300–0G960499, 0D082000–0G303045
Mercury	V-150 (EFI)	150	N/A	0G960500–0T408999	27-991734	Also confirmed for 0G303046–0G760299, 0G760300–0G960499, 0D082000–0G303045
Mercury	V-150 DFI (2.5L)	150	2-Stroke	0G960500–1B417702 & Up	27-991734	Covers various serial ranges including 0T178500–0T800999, 0T801000–1B226999, 1B227000–1B417701
Mercury	V-150 EFI (2.5L)	150	2-Stroke	0T409000–Up	27-991734	Covers various serial ranges including 0T801000–1B226999, 1B227000 & Up
Mercury	V-150XRI (EFI)	150	N/A	0D082000–0G303045	27-991734
Mercury	V-175	175	N/A	0G303046–0G960499	27-991734	Also confirmed for 0D082000–0G303045
Mercury	V-175 (EFI)	175	N/A	0G960500–0T408999	27-991734	Also confirmed for 0G303046–0G760299, 0G760300–0G960499, 0D082000–0G303045
Mercury	V-175 DFI (2.5L)	175	2-Stroke	0T178500–1B417702 & Up	27-991734	Covers various serial ranges including 0T801000–1B226999, 1B227000–1B417701
Mercury	V-175 EFI (2.5L)	175	2-Stroke	0T409000–0T800999	27-991734
Mercury	V-175XRI (EFI)	175	N/A	0D082000–0G303045	27-991734
Mercury	V-200	200	N/A	0G960500–1B226999	27-991734	Also confirmed for 5624878–0C100860, 0G303046–0G760299, 0G760300–0G960499, 0D082000–0G303045
Mercury	V-200 (EFI)	200	N/A	0G960500–0T408999	27-991734	Also confirmed for 0G303046–0G760299, 0G760300–0G960499, 0D082000–0G303045
Mercury	V-200 EFI (2.5L)	200	2-Stroke	0T409000–Up	27-991734	Covers various serial ranges including 0T801000–1B226999, 1B227000 & Up
Mercury	V-200XRI (EFI)	200	N/A	0D082000–0G303045	27-991734
Mercury	XR-6	N/A	N/A	0G960500–1B226999	27-991734	Also confirmed for 0G303046–0G760299, 0G760300–0G960499, 0D082000–0G303045
Mercury	105 JET	105	N/A	0D082000–0G760299	27-991734	Also confirmed for 0G303046–0G760299
Mercury	110 Jet (2.5L)	110	2-Stroke	1B690542 & Up	27-991734
Mercury	140 JET	140	N/A	0G960500–0T178499	27-991734	Also confirmed for 0G303046–0G760299, 0G760300–0G960499, 0D082000–0G303045
Mercury	150 Pro XS (2.5L)	150	2-Stroke	1B690542 & Up	27-991734
Mercury	175 PROXS (2.5L)	175	2-Stroke	1B516339 & Up	27-991734
Mercury	200XS DFI (2.5L)	200	2-Stroke	0T235000–1E002110	27-991734	Covers various serial ranges including 0T818181–1E000796
Mercury	200XS DFI (2.5L) ROS	200	2-Stroke	1E050852 & Up	27-991734
Mercury	200XS SST	200	2-Stroke	1E050629 & Up	27-991734
Mercury	225 EFI PRO MAX/SUPER MAG	225	N/A	0G857000–0T429939	27-991734
Mercury	225X EFI PROMAX	225	N/A	0T430254–0T819605	27-991734
Mariner	ALL	105-225	N/A	1978–2005 (specific serials)	27-991734	Also listed with 3.125 Bore 2L 135 1986-2000 and 3.125 Bore 2L 150 1978-2005

Technical Specs

Product Type: Gasket
Installation Location: Drive Housing / Drive Shaft Housing to Exhaust Plate
Dimensions (Product): Length: 36.0 cm; Width: 24.5 cm; Height: 2.0 cm
Dimensions (Shipping Box): Length: 36.0 cm; Width: 24.5 cm; Height: 2.0 cm
Weight: 0.036 kg (0.08 lbs)
Technical Note: Built to genuine OEM material and dimensional specifications.

What’s in the Box

1 x Gasket (27-991734)

Installation Notes

Ensure the engine is off and the battery is disconnected for safety.
Drain any necessary fluids from the lower unit according to your service manual.
Carefully disassemble the lower unit to access the drive shaft housing and exhaust plate area.
Remove the old gasket and any remaining sealant or debris.
Thoroughly clean both mating surfaces. Surfaces must be clean, dry, and free of corrosion or scoring.
Position the new gasket correctly. Do not use sealant unless explicitly specified by your engine's service manual.
Reassemble all components, torquing bolts to the manufacturer's recommended specifications in the correct sequence.
After reassembly, refill fluids, reconnect the battery, and check for any leaks before operating the engine under load.

Troubleshooting & FAQ

How do I find my engine's serial number to confirm fitment?

The serial number is typically located on a plate or sticker on the transom bracket, swiveling bracket, or upper part of the engine. Refer to the compatibility table on this page to match your serial number with the listed ranges.

What are the signs of a failed drive housing gasket?

Common symptoms include water in the gearcase oil (milky-looking oil), visible water leaks from the housing joints, or exhaust fumes escaping from areas other than the propeller hub. Overheating can also occur in severe cases.

Is any gasket sealant or adhesive required for installation?

In most cases, this gasket is designed to be installed dry. The surfaces must be perfectly clean. Using sealant can sometimes cause the gasket to slip or extrude. Always follow the specific instructions in your engine's official service manual.

Can I reuse my old gasket if it looks okay?

No. Gaskets are single-use components that compress and conform to the mating surfaces. Once compressed and heat-cycled, they lose their ability to create a reliable seal and should always be replaced.

Where exactly on the engine does this gasket install?

This gasket creates the seal between the main drive shaft housing (the upper part of the lower unit) and the exhaust plate, which is part of the engine adapter plate assembly.

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 and specifications against 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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Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.

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