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Required for fitment review to confirm compatibility.
The OBR Mercury 3.0L counter-rotation lower unit is a replacement gearcase for selected Mercury 200 DFI/OptiMax, 225 and 250 HP 3.0-liter V6 outboards. This listing includes new and remanufactured configurations with 25-inch XL or 30-inch XXL driveshaft lengths, depending on the selected SKU.
The available configurations are divided between 1994–2007 and 2008–2018 application groups. These groups must not be selected using horsepower alone. Confirm the complete engine model and serial number, original gear ratio, existing shaft length and counter-rotation configuration before ordering.
This product is for a verified counter-rotation/left-hand application. It should not be selected as a replacement for a standard-rotation gearcase or an undocumented performance gearcase. The selected SKU must be reviewed against the engine and existing lower-unit information before installation.
Before dispatch, compare the selected SKU with the complete engine model and serial number, engine year group, 3.0L V6 DFI/OptiMax configuration, existing counter rotation, original gear ratio and driveshaft length. Pause the shipment and contact the customer if any information is incomplete or conflicts with the selected configuration.
Before releasing the package:
When the shipment arrives:
OBR states that gearcases ship without oil and that the first ten operating hours are critical. Its instructions require the manufacturer-specified lubricant, proper shift adjustment, varied operating speed and limited throttle during break-in. OBR break-in procedure
| Specification | Mercury 3.0L Counter-Rotation Lower Unit | 200–250 HP |
|---|---|
| Manufacturer / Brand | OBR Parts & Marine |
| Compatible Engine Make | Mercury |
| Product Family | OBR ME-G6 3.0L V6 counter-rotation lower unit |
| Conditions | New and remanufactured, depending on selected SKU |
| Engine Family | Selected Mercury 3.0L V6 two-stroke DFI / OptiMax applications |
| Horsepower Applications | Selected 200 DFI, 225 and 250 HP applications |
| Year Groups | 1994–2007 and 2008–2018, depending on selected SKU |
| Rotation | Counter rotation / left-hand |
| Driveshaft Lengths | 25-inch XL and 30-inch XXL, depending on selected SKU |
| Gear Ratio | VERIFY BEFORE PUBLISHING for each SKU |
| Spline Information | VERIFY BEFORE PUBLISHING for each SKU |
| Current SKUs | ME-G6-16A-R, ME-G6-16B-N, ME-G6-16B-R, ME-G6-17B-N and ME-G6-17B-R |
| Gear Oil | Ships without gear oil; fill with the engine manufacturer's required lubricant before operation |
| Warranty | OBR two-year limited gearcase warranty; manufacturer terms apply |
| Required Fitment Data | Complete engine model and serial number, year group, horsepower, DFI / OptiMax configuration, rotation, original gear ratio and driveshaft length |
| Major Exclusions | Do not assume compatibility with standard-rotation, Verado, TorqueMaster, TorqueMaster 2, SportMaster or other non-listed gearcases |
Start by confirming that the existing gearcase is a counter-rotation/left-hand Mercury lower unit. Rotation should be verified from the current gearcase, propeller direction, engine identification and rigging—not only from the engine’s position on the transom.
Next, match the engine to the correct application group. The variants on this page cover selected Mercury 200 DFI/OptiMax, 225 and 250 HP 3.0L V6 outboards, but the catalog separates them into 1994–2007 and 2008–2018 configurations. The year group affects the required OBR SKU.
Then confirm whether the engine uses a 25-inch XL or 30-inch XXL driveshaft. Shaft length must match the existing installation. Do not change shaft length simply because another variant is available.
Finally, verify the original gear ratio and provide the complete engine model and serial number. Horsepower, model year or external appearance alone cannot confirm that a replacement gearcase will fit. If any information conflicts with the selected SKU, pause the order until OBR or a qualified marine technician confirms the application.
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Ordering the SEI counter-rotation lower unit for my twin Mercury 3.0L 225 HP outboards was straightforward. The 1.75:1 gear ratio and 25-inch shaft matched my port side engine setup perfectly. Fitment support made sure I double-checked the engine serial number before placing the order.
Clear guidance on identifying the SE216 counter-rotation configuration versus standard rotation. The unit arrived well-packaged in a heavy-duty crate with zero shipping damage. Rated 4.5 stars because the break-in procedure requires strict adherence to fluid changes after the first 10 hours.
The 1.75:1 gear ratio and shaft length details were clearly outlined on the product page. Swapping out my damaged port side gearcase was seamless. Everything aligned cleanly with the driveshaft splines and shift linkage.
The serial number verification requirement gave me complete peace of mind that I was getting the right counter-rotation lower unit for a 3.0L Mercury 225 HP. Bolted right up to the midsection without issue.
Great customer support from Mariners Warehouse. They helped confirm shaft length and counter-rotation prop shaft fitment prior to checkout. Runs quiet and shifts smooth across all throttle ranges.
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