ZF 305-3 Marine Gearbox: Hydraulic Reverse Reduction with SuperShift
Delivering smooth, reliable power transfer for high-performance yachts and light commercial vessels with lightweight aluminum construction and full twin-engine symmetry.
At Wave Inboard Motors, we’ve supplied and installed hundreds of ZF 305-3 (and 305-3 A) marine gearboxes over the past 20 years, pairing them with engines from 300-600hp in twin setups for everything from 40ft express cruisers to light-duty trawlers and sportfishers. As authorized ZF marine specialists, we value the 305-3’s robust yet lightweight design—seawater-resistant aluminum casing, case-hardened gears, and thrust bearings engineered for maximum propeller loads. If you’re planning a marine engine installation service or gearbox swap, our team ensures perfect alignment and SuperShift calibration for buttery-smooth shifts. The ZF 305-3 is the go-to reverse reduction transmission for pleasure craft and light commercial applications, offering 11 ratios from 1.000:1 to 2.917:1 with identical torque capacity ahead and astern—ideal for balanced twins.
This hydraulic multi-disc clutch gearbox stands out for its fully works-tested reliability, replaceable oil filter, and compatibility with waterjets or surface-piercing props. ISO 9001 compliant and featuring the renowned SuperShift clutch for rapid, precise engagement, it’s a favorite in luxury motoryachts, sport fishers, and express cruisers—backed by our boat repower consultation data showing near-zero failures in properly maintained units.
Technical Specifications
| Specification | Details |
|---|---|
| Type | Reverse reduction hydraulic multi-disc clutches |
| Casing | Lightweight seawater-resistant aluminum alloy |
| Gear Design | Case hardened & ground for long life/smooth run |
| Thrust Bearing | Full propeller thrust ahead/astern |
| Shifting | Hydraulic with SuperShift control |
| Twin Install Symmetry | Same ratio/torque ahead & astern |
| Oil Filter | Replaceable cartridge |
| Available Ratios | 1.000, 1.220, 1.486, 1.758, 1.968, 2.250, 2.500, 2.917:1 (specials: 0.884, 0.923, 1.297:1) |
| Down Angle | 7° or 8° (model dependent) |
| Max Input Torque | ~1,200-1,500 Nm (engine dependent) |
| Actuators | Mechanical MB30-1 or Electric EB31 (12V/24V) |
| Weight (dry, approx.) | 250-300 kg |
Competitor Comparison
| Feature | ZF 305-3 / 305-3 A | Twin Disc MG-5050 | PRM 1000 |
|---|---|---|---|
| Type | Hydraulic multi-disc SuperShift | Mechanical/hydraulic QuickShift | Hydraulic full powershift |
| Ratios | 11 (incl. specials) | 6-8 typical | 6-8 |
| Weight | ~280 kg | ~350 kg | ~320 kg |
| Twin Symmetry | Full | Good | Excellent |
| Trolling Option | Mechanical/electric kits | Standard | Standard |
| Duty Rating | Pleasure + light commercial | Commercial medium-duty | Pleasure/commercial |
| Special Features | Live PTO, monitoring kits, Vulkan couplings | Robust for workboats | Simple design |
Verdict: The ZF 305-3 wins for high-performance pleasure craft and light-duty twins with its extensive ratio selection, SuperShift speed, and lightweight build—perfect where smooth shifting and twin symmetry matter. Twin Disc MG-5050 for heavier commercial, PRM 1000 for budget reliability, but the 305-3’s aluminum durability and options like electric trolling make it the top all-rounder. As our superyacht propulsion systems guide notes, ZF dominates this power band.
Replacement Options
| Factor | Keep Old Gearbox (e.g., ZF 280/220) | Buy New ZF 305-3 / 305-3 A | Closest Modern Equivalent: Twin Disc MGX-5050 |
|---|---|---|---|
| Condition | Fair (clutch wear, seals) | Excellent (factory fresh) | Excellent (updated seals) |
| Warranty | Expired | 2 years | 2 years commercial |
| Ratios/Torque Symmetry | Limited | Full twin symmetry, 11 ratios | Good symmetry, fewer ratios |
| Features | Basic | SuperShift, trolling, PTO | QuickShift standard |
| Total Project Value | Low ($0 upfront, repairs rising) | Medium ($8,500-$12,500 incl. install) | Higher ($10,000-$14,000, heavier duty) |
Expert Recommendation: For 300-600hp twin pleasure or light commercial boats, a new ZF 305-3 is usually the best drop-in—wide ratios and SuperShift future-proof your setup. Twin Disc MGX-5050 for tougher duty, but the 305-3’s lightness and our ZF expertise deliver superior ROI. Signs of age? Our replacing an old marine diesel engine (and gearbox) guide helps decide.
Pros and Cons
| Pros | Cons |
|---|---|
| Lightweight aluminum (sea water resistant) | Max torque ~1,500 Nm (check rating) |
| SuperShift for fast, smooth engagement | Electric actuator/trolling extra cost |
| 11 ratios incl. specials for perfect prop match | Not for extreme heavy-duty (see ZF 3000) |
| Full twin symmetry | Special ratios add lead time |
| Trolling valve & live PTO options | Hydraulic needs clean oil/filters |
Frequently Asked Questions (FAQs) About the ZF 305-3 Marine Gearbox
From our 200+ ZF service calls—quick answers for owners.
What boats suit the ZF 305-3 best?
Luxury motoryachts, sport fishers, express cruisers, and light-duty workboats—twin installs 300-600hp.
Popular ratios for ZF 305-3 A?
1.486:1, 1.758:1, 2.250:1, 2.500:1 most common; specials like 1.297:1 or 2.917:1 available.
SuperShift clutch—what’s the advantage?
Faster, smoother shifts with less wear—great for frequent maneuvering.
Trolling valve worth adding?
Yes for fishing—drops speed to 2-3 knots; mechanical or 12/24V electric kits.
Competitors to ZF 305-3?
Twin Disc MG-5050 (heavier duty), PRM 1000 (budget), Velvet Drive—ZF wins on weight/ratios.
Maintenance schedule for ZF 305-3?
Oil/filter every 250-500 hours; full service 1,000 hours—our Volvo parts & maintenance stocks kits.
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