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Required for fitment review to confirm compatibility.
This OBR Mercury 70–90 HP 3-cylinder lower unit is a replacement gearcase for selected Mercury and Mariner outboards. The available configurations combine new or remanufactured condition with either the earlier 3-jaw clutch group or the later 6-jaw clutch group. Every option on this page uses a 20-inch L driveshaft.
Select the 3-jaw configuration for the OBR 1987–1997 application group or the 6-jaw configuration for the 1998–2010 group, then submit the complete engine model and serial number for fitment review. Horsepower and model year alone are not sufficient to confirm compatibility.
New OBR gearcases are assembled using new OEM and new aftermarket components. In OBR’s remanufactured units, the seals, bearings and gears are replaced with new parts. The water pump is not included, and the gearcase ships without gear oil.
Do not select this lower unit by horsepower or model year alone.
Before ordering, confirm:
A 6-jaw gearcase must not be substituted for a 3-jaw application unless the required updated Mercury shift rod and the complete conversion procedure have been confirmed by a qualified marine technician.
This gearcase ships without gear oil. Before installation or operation, fill it to the engine manufacturer’s specified level using the required marine gear lubricant.
Confirm the selected condition, clutch style, 20-inch driveshaft, and submitted engine model and serial number before shipment. If the fitment information is incomplete or conflicts with the selected variant, the order should be held for clarification.
After installation, proper idle speed and shift adjustment are essential. Avoid full-throttle starts, vary operating speed during break-in, and do not exceed 75% throttle during the first five operating hours. During the following five hours, do not maintain full throttle for extended periods.
Inspect the package and gearcase promptly after delivery. Contact Mariners Warehouse immediately if transit damage is found.
| Specification | Mercury 70–90 HP 3-Cylinder Lower Unit | 20 INCH L | 3- or 6-Jaw |
|---|---|
| Manufacturer | OBR Parts & Marine, Inc. |
| Brand | OBR |
| Compatible Engine Make | Selected Mercury and Mariner applications |
| Product Type | Replacement outboard lower-unit / gearcase assembly |
| Engine Family | Selected 70–90 HP three-cylinder applications |
| Condition Options | New or remanufactured |
| Clutch-Jaw Options | 3-jaw or 6-jaw, depending on engine year and configuration |
| 3-Jaw Application Years | 1987–1997 |
| New 3-Jaw SKU | ME-G3-06-N |
| Remanufactured 3-Jaw SKU | ME-G3-06-R |
| 6-Jaw Application Years | 1998–2010 |
| New 6-Jaw SKU | ME-G3-07-N |
| Remanufactured 6-Jaw SKU | ME-G3-07-R |
| Driveshaft Length | 20-inch L only |
| New-Unit Construction | Combination of new OEM and new aftermarket components |
| Remanufactured-Unit Construction | Seals, bearings and required internal wear components are replaced during the remanufacturing process |
| Water Pump | Not included; sold separately |
| Gear Oil | Ships without gear oil; fill before operation |
| Warranty | Two-year OBR limited warranty; terms and exclusions apply |
| 3-to-6-Jaw Conversion | Requires an updated Mercury shift rod and a confirmed conversion procedure |
| Required Fitment Information | Complete engine model number and serial number |
| Major Exclusions | Do not use for 110–125 HP L4, 25-inch XL, Optimax, DFI or four-stroke applications without written fitment confirmation |
The clutch configuration is one of the most important selection points for this Mercury 70–90 HP three-cylinder lower unit. OBR assigns the ME-G3-06 family to the 3-jaw 1987–1997 application group and the ME-G3-07 family to the 6-jaw 1998–2010 group. However, the year range should be used to narrow the choice—not as final proof of fitment.
Compare the replacement with the existing gearcase and submit the complete engine model and serial number before checkout. If the clutch style cannot be identified externally, request a fitment review and provide clear photographs of the existing gearcase and its identification markings.
A later 6-jaw gearcase may replace an earlier 3-jaw unit only when the required Mercury shift-rod update and the complete conversion procedure have been confirmed. Do not assume that the conversion is automatic.
Every variant on this page uses a 20-inch L driveshaft. Choose a different product family for a 25-inch XL shaft, 110–125 HP L4 engine, Optimax application or Mercury four-stroke.
Use CTRL + F or search below to find your engine model
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The product information made it easy to distinguish between the 3-jaw and 6-jaw clutch lower unit configurations for my Mercury 90 HP 3-cylinder outboard. The 2.33:1 ratio, 20-inch L shaft, and serial number requirements were clearly explained.
I appreciated that the OBR 70-90 HP lower unit page specifically noted the differences in clutch jaw designs. Selecting the 20-inch shaft model was straightforward, and Mariners Warehouse fitment assistance confirmed my engine year prior to purchase.
The lower unit arrived securely packed in heavy-duty foam casing. The drive shaft splines and 20-inch shaft lined up perfectly on my 3-cylinder 90 HP engine. Shifts clean and runs smooth after completing the break-in hours.
Matching the gear ratio and checking the jaw type was essential for my Mercury 70 HP outboard. The gearcase functions great on the water, though unbolting the shipping bracket was a bit cumbersome during installation.
Replaced the worn gearcase on my Mercury 80 HP 3-cylinder. The product listing clearly detailed fitment warnings and shaft length parameters. After following the required gear lube fill steps, it has run without issue.
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