--- title: "Lower Unit Repair Miami FL | Gearcase & Seals" url: "https://www.boatrepairmiamifl.com/services/boat-lower-unit-repair/" description: "Lower unit and gearcase repair in Miami. Seal replacement, gear oil, water pump impellers, and full rebuilds for outboards and sterndrives." --- 1. [Home](https://www.boatrepairmiamifl.com/) 2. [Services](https://www.boatrepairmiamifl.com/services/) 3. Lower Unit & Gearcase Repair Miami # Boat Lower Unit & Gearcase Repair in Miami Gearcase service, seal replacement, gear oil, water pump impellers, shift shaft, and pinion bearing repair [Request Service](https://www.boatrepairmiamifl.com/contact-us/) [Call (305) 290-2701](tel:+13052902701) Nothing eats an outboard or sterndrive faster than water in the lower unit. Milky gear oil at the annual check means seals are leaking, and seals that leak now will destroy bearings and gears if not addressed. We service lower units from simple gear oil changes to complete rebuilds. ## Annual Lower Unit Service Every outboard and sterndrive should have gear oil changed at least once a year, more often for heavy use. The annual service includes: - Drain and visually inspect old gear oil - Check for water intrusion (milky color) - Check for metal shavings (bearing or gear wear) - Refill with manufacturer-spec gear lube - Pressure test drain plug seals - Water pump impeller inspection - Anode (zinc) replacement - Prop shaft seal inspection ## Water Pump Impeller Replacement The water pump impeller lives inside the lower unit and circulates cooling water to the engine. Impellers dry out, crack, and lose vanes with age. A failed impeller lets the engine overheat within minutes. We recommend impeller replacement every 2 years minimum, annually for heavy-use boats. During replacement we also inspect the water pump housing, pump liner, and cooling passages. ## Lower Unit Seal Replacement When gear oil comes out milky, seals are leaking. Common seal jobs include: - Prop shaft seal (most common failure, usually from fishing line wrapped around the shaft) - Drive shaft seal (harder access, requires gearcase removal) - Shift shaft seal - Pinion shaft seal We replace seals properly, which often means full gearcase disassembly to reach the drive shaft seal. Not the fun kind of work, but done right once it lasts years. ## Gearcase Rebuild When water intrusion has gone unaddressed long enough, bearings and gears start pitting. That is where a gearcase rebuild happens. Full rebuild includes: - Complete disassembly - Clean and inspect every gear, bearing, and shaft - Replace failed bearings (forward, reverse, pinion, drive shaft) - Replace all seals - Replace shift dog if worn - Lap or replace gears if pitted - Reassemble with proper shim stack (backlash measurement) - Pressure test before reinstall ## When Lower Unit Work Needs Haul-Out Most lower unit service on outboards can be done at the dock with the motor tilted up. Sterndrive gearcase work usually requires haul-out since the drive has to come off the boat. We coordinate haul at partner yards as needed. ## Lower Unit Problems We Fix - Milky gear oil (water intrusion) - Metal shavings in gear oil (bearing wear) - Whining or grinding from the lower unit - Hard shifting or no shift - Popping out of gear under load - Vibration that increases with RPM - Overheating (water pump failure) - Corroded drain plugs that wont come out Lower unit problems only get worse. Catch them at the annual service and they are usually minor. Ignore them and they become a rebuild. Call [(305) 290-2701](tel:+13052902701) or [request service](https://www.boatrepairmiamifl.com/contact-us/). Know the Signs ## Signs Your Lower Unit Needs Service Milky or cream-colored gear oil Metal particles or shavings in gear oil Whining, grinding, or clunking from lower unit Hard shifting or refusing to shift Popping out of gear under load Overheating (temperature alarm) Vibration increasing with RPM Water leaking from drain plug area Our Process ## Our Lower Unit Service Process 1 ### Oil Drain & Inspection Drain gear oil, check color and metal content. Pressure-test the gearcase if water is present. 2 ### Water Pump Check Pull water pump housing, inspect impeller, and replace if due. 3 ### Seal & Bearing Service Replace failed seals. If bearings have spun, schedule a full rebuild. 4 ### Refill & Test Fill with manufacturer-spec gear lube, replace anodes, sea-trial under load. Miami Lower Unit Specialists ## Saltwater Kills Lower Units Fast Miami saltwater and tropical heat accelerate lower unit wear. Prop shaft seals fail faster because fishing line wraps on the shaft corrode seal faces. Gear oil breaks down quicker in hot water. Water pump impellers dry out during long dock sit periods in summer heat. Our team knows the specific lower unit failure modes for Miami-based Mercury, Yamaha, Suzuki, Honda, and MerCruiser drives. Why Choose Us ## Why Choose Our Lower Unit Service Annual gear oil service for outboards and sterndrives Water pump impeller replacement Prop shaft, drive shaft, and shift shaft seal replacement Full gearcase rebuild with bearings and gears Anode replacement and pressure testing Mobile service for most outboard work, shop for sterndrive gearcase ## Lower Unit & Gearcase FAQ Common questions about lower unit & gearcase in Miami At least annually. Miami boats that run often should change it every 50-100 hours. Fresh clean oil is cheap insurance against seal and bearing failure. Water intrusion from failed seals. The water mixes with gear oil and turns it cream-colored. Run the motor with milky oil long enough and bearings pit, gears score, and the repair goes from a seal job to a full rebuild. Every 2 years minimum, annually for heavy-use boats. Impellers dry out even when not being used and crack when spun after a dry sit. A failed impeller can overheat the motor within 5 minutes of running. Most lower units are rebuildable if the housing is not cracked. New bearings, new gears, new seals, proper shim setup, and it is back to like-new. Complete replacement is usually only necessary for catastrophic damage or when rebuild cost approaches replacement cost. More Services ## Related Boat Repair Services [### Inboard Engine Repair Inboard and marine diesel service for cruisers, sportfishers, and express yachts. 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