SE109 vs SE117 OMC Cobra Lower Units Compared
SE109 vs SE117 OMC Cobra Lower Units
A side-by-side breakdown of the standard-rotation SE109 and counter-rotation SE117 replacement lower units — so you order the correct one the first time.
The SE109 vs SE117 Decision Point
Once you've confirmed you're dealing with an OMC Cobra sterndrive lower unit and you're ready to order an OMC Cobra lower unit replacement, there's one decision that trips up more owners than any other: rotation. Order the wrong rotation and the replacement won't function correctly with your existing setup — even though the drive family, mounting, and general appearance are correct.
This article compares the two rotation-specific replacement options — the SE109 OMC Cobra lower unit and the SE117 OMC Cobra lower unit — side by side, so you can confirm which one matches your boat before you place an order.
SE109 and SE117 at a Glance
SE109
The SE109 OMC Cobra lower unit is the OMC Cobra standard-rotation lower unit option, listed under MPN 90-109-02.
It's commonly cross-referenced to OE number 0985586 — meaning it's frequently used as a replacement where that OE number applies, not that it's a guaranteed match for every application carrying that number. Always confirm your own OE number against your removed unit before ordering.
The SE109 is generally the option owners reach for on single-engine boats, since most single-engine OMC Cobra applications run standard rotation. On a twin-engine setup, don't assume both sides need the same part — one side of a counter-rotating pair typically calls for the SE117 instead, covered next.
- Rotation: Standard
- MPN: 90-109-02
- Commonly cross-referenced to: 0985586
SE117
The SE117 OMC Cobra lower unit is the OMC Cobra counter-rotation lower unit option, listed under MPN 90-117-02.
It's commonly cross-referenced to OE number 0985497, used where a counter-rotation OMC Cobra replacement gearcase is required — most often on twin-engine setups. As with the SE109, cross-reference your own OE number before ordering.
On a twin-engine boat, the two drives are usually paired so one turns standard and the other turns counter, which helps balance torque and steering feel at the helm. Ordering two SE109 units, or two SE117 units, for a paired twin-engine setup is a common and avoidable mistake.
- Rotation: Counter
- MPN: 90-117-02
- Commonly cross-referenced to: 0985497
SE109 vs SE117: Side-by-Side Comparison
| Feature | SE109 | SE117 |
|---|---|---|
| Rotation | Standard rotation | Counter rotation |
| MPN | 90-109-02 | 90-117-02 |
| OE Reference | Commonly cross-referenced to 0985586 | Commonly cross-referenced to 0985497 |
| Typical Use Case | Single-engine setups or the standard-rotation side of a twin-engine pair | Counter-rotation side of a twin-engine setup, where opposite prop rotation is required |
| What's Excluded | Confirm separately what hardware, trim components, or fasteners are included with your specific order — not assumed to include every accessory from your original unit | Same as SE109 — confirm inclusions separately rather than assuming a full one-to-one accessory match |
What's Excluded and What to Check Before Ordering
Neither the SE109 nor the SE117 should be treated as a drop-in match for every OMC Cobra application without a quick confirmation step first. Before ordering, check the following:
- Match your OE number (for example, from your original drive's tag or casting) against the cross-reference listed above, rather than assuming it based on rotation alone.
- Confirm your rotation direction using the guidance in the FAQ below — don't guess based on which side of the boat the engine sits on.
- Check what's included with the specific listing (hardware, gaskets, trim tabs, etc.) rather than assuming everything from your old unit is included automatically.
- On a twin-engine boat, confirm you're ordering one SE109 and one SE117 if your setup uses a counter-rotating pair — not two of the same part.
- If you removed a lower unit that doesn't clearly match either MPN's cross-reference, reach out before ordering rather than guessing.
Taking a few minutes on these checks up front is far less costly than sending a part back and starting over. If you're at all unsure after going through this list, it's worth having someone confirm your OE number and rotation before you commit to an order.
Frequently Asked Questions
What's the difference between SE109 and SE117?
The core difference is rotation. The SE109 is the standard-rotation option (MPN 90-109-02, commonly cross-referenced to 0985586), while the SE117 is the counter-rotation option (MPN 90-117-02, commonly cross-referenced to 0985497). Both are built for the OMC Cobra family — the deciding factor between them is which rotation direction your application requires.
Does SE109 replace King Cobra?
The SE109 is built as a replacement within the OMC Cobra lineup, cross-referenced to OE number 0985586. King Cobra is a separate drive family with its own case and shift characteristics, so the SE109 isn't intended for King Cobra applications. If you're not certain which family your original lower unit belongs to, compare your case and OE number carefully — or reach out — before assuming either part fits.
How do I know if I need standard or counter rotation?
Rotation is typically tied to how your propeller shaft turns and, on twin-engine boats, how the two drives are paired to counteract torque. Rather than guessing, compare your removed lower unit's OE number against the cross-references listed above, check any tag or casting markings on the original unit, or confirm rotation with a technician before ordering. Ordering the wrong rotation is one of the most common — and most avoidable — mistakes when replacing an OMC Cobra lower unit.
Confirm Rotation and OE Number Before You Order
The SE109 and SE117 solve two different problems — getting them mixed up is the single most common mistake owners make when replacing an OMC Cobra lower unit. Double-check your rotation direction and OE number against what's listed above, and if anything's unclear, ask before you buy.
Not sure which drive family you have at all? Start here: How to Identify an OMC Cobra Lower Unit