# 125018 O-Ring | Genuine Volvo Penta Part

## 🔧 Product Description

This is a genuine Volvo Penta O-ring seal in the 29.7 x 3.53 mm size, supplied as the late-design version of the seal for this location. It provides a static sealing joint between mating components on a broad group of classic Volvo Penta petrol and diesel marine engines and their drive assemblies. Because O-rings of the same generic name differ only by section and diameter, confirm the 29.7 x 3.53 mm dimension before ordering.

## 🚤 Compatibility

-   **Engine Family:** AQ, MD, TMD, AD, AQAD, BB, TAMD, MS, B, AQD, MB
-   **Year Range:** Approximately 1970s-1980s

Full model list at the end of this description.

## ⚙️ Key Features

-   OEM Volvo Penta part number 125018
-   Dimension: 29.7 x 3.53 mm
-   Late-design (later production) version of the seal
-   Fits classic Volvo Penta AQ, MD, TMD, TAMD, AD, BB, MB and MS series marine petrol and diesel engines
-   Supplied as a single O-ring
-   System type: Internal clutch, shaft or gear-housing oil seal
-   8 used per assembly

## 🔌 Function

The O-ring forms a compressed static seal between two mating surfaces or around a shaft or fitting, preventing oil, coolant, fuel or water from escaping the joint. Correct section thickness and inside diameter are essential for the seal to seat and hold pressure.

## ⚠️ Common Signs of Failure

-   Weeping or dripping fluid at the joint the O-ring seals
-   Hardened, cracked or flattened rubber that has lost its round cross-section
-   Swollen or softened material from fluid or heat degradation
-   Loss of system pressure or air being drawn into the joint
-   Visible nicks, cuts or extrusion of the ring from its groove during disassembly

## 🛠️ Service Notes

-   Always fit a new O-ring — never refit one that has been removed, as it has already taken a set in its groove
-   Clean the groove and both sealing faces and check them for nicks, scoring and corrosion pitting; a damaged groove will leak however good the new seal is
-   Smear the ring with a little clean lubricant compatible with the fluid it seals, then roll it into place by hand so it sits untwisted and fully in its groove
-   Never lever an O-ring over a sharp edge or thread with a screwdriver; use a blunt plastic tool and protect any edge the ring has to pass
-   Assemble the joint squarely and tighten to the figure and sequence given in the workshop manual for your engine — over-tightening extrudes the ring and causes the very leak you were curing

## 🔄 Supersession & Cross Reference

### OEM / Related Numbers

-   875628 earlier MS3 gasket kit
-   876400 later MS3 gasket kit
-   850413 MS3 reverse gear, ratio 1.91:1
-   850417 related slip clutch
-   852072 related slip clutch
-   925256 companion O-rings
-   925069 companion O-rings
-   942353 companion O-rings
-   958879 related sealing ring

## 📦 Condition

-   Genuine Volvo Penta part
-   Brand new
-   Supplied in original or equivalent packaging

## 🔎 Full Model Compatibility

Typically suits:

-   Volvo Penta AQ130C, AQ130D, AQ130A, AQ130B
-   Volvo Penta AQ170B, AQ170C, AQ170A
-   Volvo Penta BB115A, BB115B, BB115C
-   Volvo Penta BB170B, BB170C, BB170A
-   Volvo Penta BB260AV, BB260B, BB260C
-   Volvo Penta MB20A, MB20B, MB20C
-   Volvo Penta TMD40A, TMD40B, TMD40C
-   Volvo Penta AQ115A, AQ115B
-   Volvo Penta AQ260A, AQ260B
-   Volvo Penta AQAD40B, AQAD40A
-   Volvo Penta AQD21A, AQD21B
-   Volvo Penta MD21B, MD21A
-   Volvo Penta MS3B, MS3C
-   Volvo Penta 100S, 110S
-   Volvo Penta TAMD40A, TAMD40B
-   Volvo Penta AD40B
-   Volvo Penta AQ120B
-   Volvo Penta AQ125A
-   Volvo Penta AQ140A
-   Volvo Penta AQ165A
-   Volvo Penta AQD40A
-   Volvo Penta B20
-   Volvo Penta BB140A
-   Volvo Penta BB145A
-   Volvo Penta BB165A
-   Volvo Penta MD30A
-   Volvo Penta MD40A
-   Volvo Penta TAMD30A
-   Volvo Penta TMD30A

## Details

- **Price:** 48.19 AUD
- **Vendor:** Volvo Penta
- **Type:** Gaskets & Seals
- **Tags:** Volvo Penta Parts | Genuine Marine Engine & Service Components

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| Default Title | 48.19 AUD | In stock |

## Images

- 125018 O-Ring | Genuine Volvo Penta Part

---

> Source: [Sawley's Auto and Marine](https://www.sawleysautoandmarine.com.au/products/125018-o-ring-genuine-volvo-penta)
> Updated: 2026-09-20