OMC Johnson Evinrude NEW OEM 303347 O-Ring .445 ID Gearcase (LOT OF 3) 0810

OMC Johnson Evinrude O-Ring — Part Number 303347

Brand: OMC Johnson Evinrude | Condition: New Old Stock (NOS)

Genuine OMC factory part number 303347 (also catalogued as 0303347), an O-ring measuring 0.445 in inside diameter × 0.090 in cross-section, used in the gearcase of Johnson and Evinrude outboards. OMC dealers catalogue it variously as the lower bearing O-ring, the shock cylinder O-ring and the drive shaft O-ring seal — all describing the same ring in the lower unit. This is new old stock from long-term dealer inventory, a genuine OMC component rather than a generic ring from an assortment box.

This is a lower unit sealing ring, which means its job is keeping gear lubricant in and water out. Once it hardens and takes a set, water finds its way past, the gear oil turns milky, and the bearings and gears in the gearcase corrode from the inside. A dollar's worth of rubber protects a lower unit that is not cheap to rebuild — which is why these rings are replaced on sight whenever the gearcase is opened rather than reused.

What makes it worth having on the shelf is the breadth of the interchange. The same ring is catalogued under OMC, Mercury, MerCruiser, Volvo Penta and the main aftermarket houses, and it spans a very long period of OMC production — reported from the mid-1950s through the 1970s on the small and mid-range motors, and still appearing in gearcase fiches on motors built in the 2000s.

Condition Details

New old stock. The O-ring is unused and has never been installed. As with all warehouse-stored inventory, the packaging may show shelf wear, dust, fading, price stickers, scuffs or minor crushing from stacking; OMC small rubber parts of this era were commonly supplied in plain dealer bags rather than branded blister packs. The ring itself is round, supple and uncreased, with no flat spots, splits or compression set from storage. Elastomer seals do have a finite shelf life, so we recommend inspecting the ring on arrival and before installation. Please review all photos, as what is pictured is what you will receive.

Specifications

• Part Number: 303347 (OMC long form 0303347)
• Part Name: O-Ring — catalogued by dealers as lower bearing / shock cylinder / drive shaft O-ring
• Manufacturer: OMC (Outboard Marine Corporation), later BRP
• Inside Diameter: 0.445 in (11.3 mm)
• Cross Section: 0.090 in (2.4 mm)
• Material: rubber elastomer
• Assembly Group: Gearcase / lower unit
• Sold: see listing quantity
• Genuine OEM, not aftermarket

Superseded & Cross Reference Part Numbers

OMC 303347 interchanges with the following. Always confirm against your own application guide before ordering.

• OMC / Johnson / Evinrude: 303347, 0303347
• Sierra Marine: 18-7180 (also supplied as 18-7180-9, a pack of 5)
• GLM Products: 45030
• Mercury Marine: 25-26802
• MerCruiser: several variants
• Volvo Penta: 925055
• Mallory Marine: 9-76556

If your parts list or counter quote shows Sierra 18-7180, GLM 45030, Mercury 25-26802 or Volvo Penta 925055, this listing is the genuine OMC original for that reference.

Features

• Genuine OMC factory part, made to the original material and dimensional specification
• Precise 0.445 in bore with a 0.090 in section, so it seats and compresses exactly as the groove was machined for
• Correct elastomer compound for gear lube on one side and prolonged water immersion on the other, including saltwater service
• Keeps water out of the lower unit, preventing the milky-lube condition that corrodes bearings, gears and shafts
• Broad interchange — the same ring serves OMC, Mercury, MerCruiser and Volvo Penta applications under their own part numbers
• Non-metallic, so nothing to corrode or seize against the aluminium gearcase
• Single-use by design — replaced whenever the gearcase is opened, never reused
• Inexpensive insurance on a job nobody wants to do twice

Application

Used in the gearcase / lower unit of Johnson and Evinrude outboard motors. Reported and catalogued applications include:

• Johnson and Evinrude 5.5 through 25 HP, approximately 1954 through the 1970s
• Still appearing in the Gearcase group on later motors, including the Johnson 30 HP, 2001, model J30EVLSIA
• Mercury, MerCruiser and Volvo Penta applications under the cross-reference numbers above

OMC used this ring size across a very long production span and in more than one position in the lower unit, which is why three different dealer descriptions exist for it. Buyers should confirm 303347 — or the cross-reference number for their brand — against the exploded gearcase diagram for their specific motor and year before ordering. The surest method is to measure the ring you are replacing: ID 0.445 in and cross-section 0.090 in. If you send us your model number and year we will check it against the parts catalogue for you.

Why Choose OMC Johnson Evinrude?

Outboard Marine Corporation built Johnson and Evinrude outboards for most of the twentieth century and set the standard for American two-stroke outboard engineering. OMC-numbered parts were manufactured to tight factory tolerances and specified for the marine environment, which is why decades-old OMC motors are still running today. On an O-ring the dimensions are easy to match from a chart; what is not easy to match is the compound, which has to stay flexible in gear oil and salt water for years rather than hardening and letting water into the lower unit.

Returns

We accept returns through eBay's standard 30-day return request process. If the part is not what you need, simply open a return request through eBay within 30 days of delivery and we will take care of it.

Thank you for looking. We are a small parts business and we take real care in identifying, describing and packing every item we list. If anything about this part is unclear, or if you want additional photos or measurements before you buy, please message us — we would much rather answer a question up front than have you receive something that is not right for your machine.

If there is any problem at all with your order, please contact us first and give us the chance to make it right before leaving feedback. We respond quickly and we will resolve it.

QBS Parts, Inc — Gardena, CA