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Shop outboard lower units by engine brand, including available new, remanufactured and aftermarket replacement gearcases for Mercury, Yamaha, Suzuki, and Evinrude/Johnson applications. Verify the model, serial number, shaft length, gear ratio and rotation before ordering.
Browse all available lower units by their engine brand and application.
Use the complete engine model and serial number to narrow the available lower unit fitment.
Confirm the required shaft length, lower unit gear ratio, and standard or counter rotation.
Review the exact application notes, included components, condition, and warranty shown on the selected product page.
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Send us the engine manufacturer, complete model number, serial number, horsepower, model year, two- or four-stroke configuration, current gearcase or part number, shaft length, gear ratio, and rotation.
Clear photos of the engine identification label and removed lower unit can also help us review the available replacement lower unit fitment before you order.
Choosing the correct replacement outboard lower unit starts with the engine identification details—not the gearcase appearance or horsepower alone. Confirm the information below, then compare it with the exact application notes on the selected product page.
Start with the engine brand and identify the exact engine family or series.
Copy the complete model and serial number directly from the engine identification label.
Confirm the required shaft length using the engine code and application information.
Match the replacement lower unit gear ratio to the verified requirement for your engine.
Determine whether the existing setup requires a standard-rotation or counter-rotation lower unit.
Record any readable gearcase, casting, or part number and review all product-specific fitment notes.
An outboard lower unit, often called an outboard gearcase, is the drive assembly below the engine’s midsection. It transfers engine power through the internal gears and propeller shaft to the propeller while also supporting steering and forward or reverse operation.
This collection is the main shopping hub for complete replacement outboard lower units—not loose internal parts, repair services, jet-drive conversion kits, or sterndrive assemblies.
Shoppers sometimes use broad terms such as boat lower units or marine lower units, but outboard motor lower units are different from sterndrive lower units. Start with Mercury, Yamaha, Suzuki, or Evinrude/Johnson, then enter the collection that matches the engine already installed on your boat.
Available products may differ by manufacturer, engine family, condition, horsepower, shaft length, gear ratio, and rotation. A product title is only a starting point. The complete model number, serial number, existing gearcase information, and product-specific application notes should control the final selection.
Product condition and product source are important, but neither determines fitment. Confirm compatibility with the engine before comparing price, condition, availability, or coverage.
A new outboard lower unit is sold as a newly manufactured replacement assembly.
A remanufactured outboard lower unit normally begins with an existing housing or core that has been restored according to the supplier’s stated process.
Aftermarket lower units are produced by a manufacturer other than the engine’s original manufacturer. “Aftermarket” identifies the product source; it does not automatically mean used or remanufactured.
A standard-rotation lower unit and a counter-rotation lower unit are different gearcase configurations. Match the rotation required by the existing engine and gearcase; do not choose a replacement from horsepower or housing appearance alone.
Twin-engine boats may use opposite-rotation lower units, but engine position by itself does not prove the required rotation. Confirm the complete engine model and serial number, current gearcase or part number, propeller rotation in forward gear using the applicable service information, and the rotation stated on the selected product page.
If any of these details disagree, request an outboard lower unit fitment review before ordering.
Available shopping paths may include Mercury BigFoot, OptiMax, Verado, Pro XS, TorqueMaster, V6, and V8 lower units.
Verify the complete model and serial number, engine family, shaft length, gear ratio, rotation, condition, and every application-specific mechanical detail.
Available shopping paths may include Yamaha F-Series, HPDI, VMAX SHO, V6, and V8 replacement lower units.
Verify the PID or complete model number, serial number, engine family, stroke configuration, shaft length, gear ratio, rotation, and condition.
Current shopping paths include listed Suzuki standard-rotation and counter-rotation lower units for selected DF200, DF225, and DF250 applications.
Verify the complete model and serial number, shaft length, required rotation, and existing gearcase information.
Available shopping paths include listed V4, V6, Magnum, standard-rotation, and counter-rotation replacement lower units.
Verify the model and serial number, current part number, drive family, gear ratio, and rotation.
Browse the dedicated OMC Cobra collection for selected standard-rotation and counter-rotation OMC Cobra lower unit applications.
Explore guides and tips related to this collection.
I was considering the SE403 jet drive conversion for a 50-60 HP four-stroke Yamaha. The listing made it obvious that this differs from a standard lower unit and that engine model, PID and included components need to be confirmed first. That warning saved me from ordering the wrong kit.
The SE404 lower unit page explained that 75-100 HP Yamaha engines can use different shaft lengths and gear ratios. Instead of relying on horsepower alone, it pushed me to match the engine model, PID and existing ratio, which made the whole selection process much safer.
The SE416 lower unit family covers a wide range of 150-225 HP Yamaha engines, and the page did a good job showing that ratios and shift configurations differ within the family. Confirming my exact model before ordering avoided a costly mismatch.
I almost picked a counter-rotation lower unit based on engine position alone, but the SE418 listing clearly said that's not enough. It asked for propeller rotation, shaft length and shift configuration to be verified, which is a detail a lot of listings skip.
Looking for an F250 lower unit, I appreciated that the SE422 listing broke down the 20-, 25- and 30-inch configurations instead of treating every F250 the same. Confirming shaft length and current gearcase first made the order accurate.
Shopping for a 115/130 HP Yamaha gearcase can get confusing since the SE405 covers several variants with different specs. The listing clearly asked buyers to verify engine family, PID and current gearcase reference before purchase, which is exactly what I needed.
Finally found the right lower unit for my early-style V4 Johnson without paying OEM prices. The 2.0:1 ratio feels spot on, and the internal water screens are the correct setup for this era of engine — a lot of sellers get that mixed up. Just make sure you confirm your upper driveshaft length first. Been running it a full season, no issues.
I almost bought the SE304 before realizing my later-style V4 needed external water screens, not internal ones. This unit's flat cavitation plate confirmed I had the right one. Same 2.0:1 ratio as expected, installed clean, and performance has been solid since. Just double-check your exact engine model before ordering — that's the part people skip.
Running this on a standard-rotation V6 and it's been dependable. The 1.83:1 ratio and Ocean Pro-style intakes are correctly matched to my engine. One heads-up: this is NOT a Magnum or Lightning replacement, so don't assume it's a universal fit. Confirm your existing case type first and you'll have zero problems.
Been putting off replacing my OMC Cobra lower unit (MPN 90-109-02) for months because of OEM pricing, finally pulled the trigger on this one. Standard rotation, matched my original gearcase exactly, and installation was straightforward once I had the right thrust washer on hand. Running strong a few months in, no leaks or noise issues.
I was searching for Mercury lower units for sale that would match my 90 HP without paying dealer prices, and the SE205 lower unit covering 70-125 HP was a perfect match. Bolted right up, shifted cleanly on the first try, and the fit and finish looked just as good as OEM. This is now my go-to source whenever I need a Mercury lower unit replacement.
My old gearcase was leaking gear oil after years of lake use, so I went looking for a replacement gearcase for my Mercury outboard. The SE90-206 unit for the 2.0L/2.4L/2.5L V6 dropped in without any modification. Shifting is smooth in forward, neutral, and reverse, and there's zero play in the prop shaft. Very happy with this purchase.
I needed to match the exact Mercury lower unit gear ratio on my 3.0L V6, and the SE90-216 with the 1.62 ratio option was spot on for my setup. Installed it myself over a weekend and took the boat out the same day. No vibration, no whine, just clean power delivery all the way to wide open throttle.
Running twin engines meant I specifically needed a Mercury counter-rotation gearcase for the starboard side. The SE90-218 matched our 3.0L V6 exactly and tracking is now dead straight with no more pulling to one side. Packaging was solid and the unit arrived with no shipping damage.
Finding an aftermarket Mercury lower unit with the correct 4.8-inch Verado bullet diameter isn't easy, but this SE90-221 unit measured out exactly right for my rig. Install took about three hours with basic hand tools. A month in and it's holding up great, no leaks and shifting is crisp.
An outboard lower unit is the gearcase assembly mounted below the engine’s midsection. It contains components that transfer engine power to the propeller shaft and support forward and reverse operation. “Outboard lower unit” and “outboard gearcase” are commonly used for the same assembly.
Possible warning signs include unusual grinding or whining noises, difficulty shifting, metal particles in the gear lubricant, water-contaminated lubricant, damaged propeller-shaft components, lubricant leakage, or visible housing damage. These symptoms should be inspected before deciding whether the lower unit requires repair or replacement.
Start with the engine manufacturer, complete model number, and serial number. Then verify the horsepower, engine family, model year or serial range, two- or four-stroke configuration, shaft length, gear ratio, rotation, and current gearcase or part number. Do not select a lower unit from horsepower or housing appearance alone.
Send the engine manufacturer, full model number, serial number, horsepower, model year, stroke configuration, shaft length, gear ratio, rotation, and any gearcase, casting, or part numbers you can locate. Clear photos of the engine identification label and removed lower unit may also help with the review.
The appropriate choice depends on the correct fitment, supplier process, included components, price, availability, core requirements, and product-specific warranty. A new or remanufactured lower unit should only be considered after its configuration has been matched to the engine.
No. “Aftermarket” normally identifies a product made by a manufacturer other than the engine’s original manufacturer. “Remanufactured” describes the condition or restoration process. An aftermarket lower unit can be sold as a new assembly.
Use the verified engine model, serial number, existing gearcase information, applicable service documentation, and the product’s fitment notes. Engines with similar horsepower can require different lower unit gear ratios, so horsepower alone is not sufficient.
Match the rotation specified for the existing engine and gearcase. On twin-engine boats, engine position alone does not prove the required rotation. Confirm the engine model, serial number, current gearcase or part number, applicable service information, and the rotation stated on the product page.
Lower unit cost varies by engine brand, engine family, horsepower, product condition, shaft length, gear ratio, rotation, and availability. Use the current product price for the selected application and check whether installation materials, lubricant, propeller components, shipping, or core charges are separate.
No. Warranty coverage can vary by manufacturer, supplier, product condition, and individual listing. Read the exact warranty information on the selected product page before ordering. Do not assume that one warranty applies to every lower unit in the collection.
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