Quick answer: To tell what OMC outdrive you have, start with the model and serial number on the drive’s ID plate. Then check the transom bracket plate and the engine’s own number. Look the model number up in an OMC stern drive lookup table or service manual to find the year. The drive’s shape also helps: Cobras have a flat-topped upper housing.
An OMC outdrive is the part of a sterndrive boat that hangs off the transom and drives the boat through the water. “OMC outdrive” and “OMC sterndrive” mean the same thing. Outboard Marine Corporation (OMC) designed and built its own line of stern drives. It did not invent the stern drive, though. OMC entered a market where Volvo and Mercury already held many stern-drive patents (Power & Motoryacht).
Problems come when the drive needs repair or replacement. A mechanic or parts seller will need to know exactly which drive you have. A guess can mean wrong parts, wasted money, and a boat that sits on the trailer.
The good news is that plenty of OMC identification help is online. That includes model-number and year lookup tables for OMC stern drives from 1964 to 1993 (MarineEngine.com). Service manuals are also sold for both the older drives and the Cobra line. This guide shows you how to use them.
What Is the Difference Between an OMC Outdrive and an OMC Cobra?
“Cobra” is not another name for every OMC outdrive. It is one OMC model line, sold from roughly 1986 to 1993. The King Cobra is part of that same family.
Older OMC stern drives, built from 1964 to 1986, are not Cobras. These include the 400 and 800 Stringer drives. Knowing which group your drive falls into is the first big step.
| OMC drive group | Approximate years | Examples | Service manual coverage |
|---|---|---|---|
| Early OMC stern drives | 1964–1986 | 400 and 800 Stringer drives | Haynes 1964–1986 OMC stern drive manual |
| Cobra family | Roughly 1986–1993 | Cobra, King Cobra | Haynes 1986–1993 OMC Cobra manual (includes King Cobra) |
How to Tell What OMC Outdrive You Have: 4 Steps
You identify an OMC outdrive by its model number and serial number. The ID plate is the best place to start, but it is not the only clue. Use these four steps together for the most reliable answer.
- Step 1: Read the ID plate on the drive. Find the identification plate on the outdrive and write down the model number and serial number exactly as shown. Take a clear photo as well. You do not need to remove the plate to read it.
- Step 2: Check the transom bracket plate. The transom bracket can carry its own plate. Record those numbers too. They help confirm what was originally installed on the boat.
- Step 3: Record the engine number. The engine has its own identification, separate from the drive. A parts seller or mechanic may ask for both, since the drive has to match the engine package.
- Step 4: Look up the numbers and check the shape. Enter your model number in an OMC stern drive lookup table or check it against a service manual. Then compare the drive’s look to what you found. For example, a Cobra has a flat-topped upper housing, while later SX units have a humped upper housing.
Keep all your numbers and photos in one place. You will need them when you call a dealer, order parts, or shop for a replacement drive.
Where Is the Serial Number on an OMC Cobra Outdrive?
The serial number is on the drive’s identification plate, next to the model number. Check the transom bracket plate as well, because it holds its own numbers. If you cannot find a plate, your service manual is the best guide to where the tags sit on your exact drive.
How Do I Tell What Year My OMC Outdrive Is?
Use the model number. Then match it in an OMC model-number lookup table, which covers OMC stern drives from 1964 to 1993 (MarineEngine.com). Service manuals and parts catalogs also list models by year.
Do not rely on the boat’s model year alone. A drive may have been replaced at some point, so the drive’s own numbers are the better guide.
How Do I Tell If My OMC Outdrive Is a 400 or 800 Stringer?
First, check the year range. The 400 and 800 Stringer drives belong to the older 1964–1986 OMC stern drives, not the Cobra line. Next, look up your model number in an OMC lookup table. Finally, confirm with the 1964–1986 OMC stern drive service manual.
What Is the Difference Between an OMC Cobra and a King Cobra?
Both belong to the same OMC Cobra family from roughly 1986 to 1993. Haynes covers them in a single service manual. To confirm which one you have, look up your model number rather than guessing from the decals, since decals can fade or be replaced.
Is an OMC Cobra the Same as a Volvo Penta SX?
No. They are different drives. One easy visual cue is the top of the upper housing. A Cobra’s top is flat. Later SX units have a humped upper housing.
Do not assume parts or whole drives will swap between them. Confirm compatibility with a parts catalog or a dealer before you buy.
How Do I Find the Gear Ratio on an OMC Cobra Outdrive?
Start with your model and serial numbers. Then check the service manual or ask a dealer to look up the drive’s specs. Do not guess. The gear ratio has to suit both your engine and your propeller. A mismatch can hurt performance even if the drive bolts on.
The same rule applies to rotation. If your boat uses a standard or counter-rotating setup, confirm which one you have before you order a drive or a prop.
What If the ID Plate Is Missing, Corroded, or Painted Over?
You can still identify the drive. Use the other clues in this order:
- Check the transom bracket plate for its own numbers.
- Record the engine number.
- Compare the drive’s shape to photos in a service manual or parts catalog. For example, check for the flat-topped Cobra housing.
- Take your notes and photos to an OMC-experienced dealer or mechanic.
If a plate is painted over, clean it gently. Harsh scraping or grinding can wipe out the stamped numbers you need.
Why You Need to Identify OMC Outdrive?
The main reason is to get the right parts or the right replacement drive. Similar-looking drives can need different parts. A correct ID saves you from ordering the wrong item.
It also helps when you talk to a mechanic. With the model number, serial number, engine number, and year in hand, they can look up the correct specs quickly. That includes the gear ratio and how the drive mates to your transom assembly.
Can You Use an OMC Outdrive if the Serial Number Is Different?
Sometimes, but do not assume it. A different serial number does not automatically mean a drive won’t fit, and a similar look does not mean it will. Fit depends on the drive model, the engine, the gear ratio, the rotation, and the transom and bell housing setup.
Before you buy a used or swapped drive, check both drives’ numbers against a parts catalog or service manual. If you are unsure, talk with a mechanic who has OMC experience.
Who Makes OMC Outdrives Now?
Outboard Marine Corporation no longer exists. Its end came in December 2000. Former executive George Broughton recalls that on December 21, 2000, Greenway Partners told staff “it was over.” OMC’s Evinrude brand was later sold to BRP (Bombardier Recreational Products) (Power & Motoryacht).
Can I Still Get Parts and Manuals for an OMC Outdrive?
Yes, reference material is still easy to find. Haynes sells a service and repair manual for the 1986–1993 OMC Cobra Stern Drive, including the King Cobra. It also sells a separate manual for 1964–1986 OMC stern drives (Haynes).
For parts, have your model number, serial number, and engine number ready before you shop. Online parts catalogs and marine dealers can match those numbers to the right parts. Since OMC closed in 2000, always confirm a part fits your exact drive before ordering.
Conclusion
To identify your OMC outdrive, read the model and serial number on the drive’s ID plate. Then check the transom bracket plate and the engine number. Look the model number up in a lookup table or service manual, and confirm it with visual cues like the housing shape. If you plan to replace the drive, match it by model, year, gear ratio, and rotation, not by looks alone. If you have no prior experience with OMC outdrives, take help from an expert before you buy or install anything.
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Frequently Asked Questions
Is an OMC outdrive the same as an OMC sterndrive?
Yes. "OMC outdrive" and "OMC sterndrive" mean the same thing. Both names describe the drive unit that hangs off the transom of a sterndrive boat and pushes it through the water. Outboard Marine Corporation designed and built its own line of these drives.
Did OMC invent the stern drive?
No. OMC designed and built its own line of stern drives, but it did not invent the stern drive. When OMC entered the market, Volvo and Mercury already held many stern-drive patents. OMC’s drives include the early 400 and 800 Stringer models and the later Cobra family.
Do I need to remove the ID plate to read my OMC outdrive numbers?
No. You can read the model number and serial number with the ID plate still on the drive. Write both numbers down exactly as shown and take a clear photo. Then record the transom bracket plate numbers and the engine number so you have every clue in one place.
Can I use my boat’s model year to date the OMC outdrive?
Not reliably. The drive may have been replaced at some point, so the boat’s model year may not match the drive. Use the drive’s own model number instead, and match it in an OMC lookup table, a service manual, or a parts catalog that lists models by year.
How should I clean a painted-over OMC outdrive ID plate?
Clean it gently. Harsh scraping or grinding can wipe out the stamped numbers you need to identify the drive. If the numbers are still unreadable, check the transom bracket plate, record the engine number, compare the housing shape to a service manual, and ask an OMC-experienced mechanic.
