Outboard parts are confusing for a reason that has nothing to do with engineering. Outboard Marine Corporation owned both Johnson and Evinrude. Volvo Penta shared sterndrive development with OMC for years. When OMC failed in 2000, Bombardier acquired Evinrude.
The practical result: a single physical o-ring can appear in four different catalogues under the same number, and your engine's brand badge tells you very little about which listing to search.
The same number really is the same part
Part 319085 is listed by OMC, by Volvo Penta, by Johnson and by Evinrude. So is 318717. So is 313446. These are not similar parts — they are the same part in different books.
- 319085 — listed under OMC / Volvo Penta
- 319085 — listed under Johnson / Evinrude
- 318717 — Johnson / Evinrude
If you find your number under a brand that isn't on your cowling, you have still found the right part.
What fails on an outboard
- Lower unit seals. Water in the gear oil. Check the oil colour at every service — milky means a seal has failed and the gearset is on borrowed time.
- Water pump housing. Impeller service is routine; the housing o-rings should be replaced at the same time rather than reused.
- Thermostat and cooling covers. Overheating alarms often trace to a hardened cover seal rather than the thermostat itself.
- Fuel system seals. Ethanol-blended fuel is hard on older elastomers. Rings that were fine for twenty years fail quickly once E10 arrives.
Winter layup is when seals die
Most outboard seals do not fail while running. They fail sitting still, compressed in one position, cold, for five months. A ring that has taken a permanent set will not recover when you launch in spring.
If your engine sits over winter, treat the first service of the season as a seal service. It is far cheaper than discovering the problem at the ramp.
Before you reassemble
Seat every o-ring with a thin film of food-grade silicone lubricant. Dry rings pinch and take a set, which is how a new seal weeps within a season. Aqua Flex Food Grade Silicone Lubricant is what ships in our kits.
O-rings only. Never lubricate the polished carbon or ceramic faces of a mechanical shaft seal — they must run dry against each other or the seal slips and leaks from new.
Beaver Island Parts Company is not affiliated with, endorsed by, or sponsored by any equipment manufacturer named on this page. All brand names, model numbers and part numbers are the property of their respective owners and are used solely to identify the equipment our replacement parts fit.