Fix Gear Case Damage Before It Spreads

Lower unit repair in Key Largo for seals, gear cases, and prop shaft issues.

When you notice milky gear oil during a routine check, hear grinding noises when shifting, or feel vibration through the steering wheel at cruising speed, your lower unit is trying to tell you something. Real Extreme Marine handles lower unit repairs throughout Key Largo, addressing the seal failures, gear wear, and impact damage that come with running in shallow water, striking submerged debris, or pushing hard through choppy conditions. The flats and nearshore zones around Key Largo are unforgiving on lower units, and even a minor prop strike can bend a shaft or crack a seal housing.

Lower unit repair involves draining the gear case, disassembling the housing, and inspecting gears, bearings, seals, and the prop shaft for wear or damage. If water has mixed with the oil, the seals are replaced and the gears are checked for pitting or corrosion. If the damage is structural, such as a cracked housing or bent shaft, you receive an honest assessment of whether repair or replacement makes more sense. Mobile service is available in Key Largo when conditions allow, so minor repairs can often be completed without hauling the boat.

If you suspect lower unit damage or want to prevent a small leak from becoming a total failure, get in touch with Real Extreme Marine to schedule an inspection in Key Largo.

How Lower Unit Damage Shows Up and Gets Fixed

When Real Extreme Marine inspects a lower unit in Key Largo, the first step is draining the gear oil and checking its condition. Clear, amber oil means the seals are intact, but milky or metallic oil indicates water intrusion or gear wear. The housing is then removed, and the prop shaft, pinion gear, and forward and reverse gears are examined under light for scoring, chips, or discoloration that signals overheating or impact damage.

After the repair is finished, your lower unit will shift smoothly between forward, neutral, and reverse without hesitation or grinding. The engine will no longer vibrate at speed, and the gear oil will stay clean between service intervals.

Repairs typically include replacing seals, O-rings, and gaskets, repacking bearings, and swapping out damaged gears or shafts. If the prop shaft is bent, it is straightened or replaced to prevent further wear on the bearings and seals. The housing is reassembled with marine-grade sealant, filled with fresh gear oil, and tested under load to confirm smooth operation. Lower unit work is precision-focused, and shortcuts during reassembly can lead to repeat failures within weeks.

What Boat Owners Usually Want to Know

People scheduling lower unit repair in Key Largo often have concerns about cost, timing, and whether the damage is severe enough to require a full replacement.

What causes lower unit seals to fail?
Seals fail from age, heat cycling, impact damage, or running the engine in shallow water where sand and debris get pulled into the cooling system. Saltwater accelerates degradation, especially on boats that sit idle for long periods.
How can I tell if my lower unit has water in the oil?
You check the gear oil during routine maintenance by removing the lower drain plug and catching a sample. If the oil looks milky, foamy, or has visible separation, water has entered the gear case and the seals need to be replaced.
What happens if I keep running the engine with a damaged lower unit?
Continuing to run with contaminated oil or worn gears will destroy the remaining components, turning a seal replacement into a full gear case rebuild. Water in the oil also corrodes internal metal surfaces, which shortens the life of any new parts installed later.
Can a bent prop shaft be straightened?
In some cases, yes, but only if the bend is minor and the shaft has not developed cracks or stress fractures. Real Extreme Marine assesses each shaft individually and recommends replacement when straightening would compromise safety or durability.
How long does a typical lower unit repair take?
Most repairs are completed within one to three days, depending on parts availability and the extent of the damage. Simple seal replacements can be done in a few hours if the unit is already removed and no other damage is found.

Lower unit damage does not improve on its own, and catching it early can save you from a much larger repair bill down the road. Contact Real Extreme Marine to schedule lower unit repair in Key Largo and protect your engine from further wear.