Investment-cast 316L stainless steel propellers for outboard, sterndrive, shaft-drive, and commercial marine applications. 3-blade and 4-blade standard; custom pitch, diameter, and OEM geometry accepted.
A marine propeller converts rotational torque into thrust by accelerating water mass astern. Its efficiency, and its service life, depends on blade geometry holding its designed pitch and cross-section over time. A propeller that deflects, corrodes, or loses surface finish degrades thrust, increases fuel consumption, and introduces vibration that eventually damages shaft seals and gearboxes.
Profab Machine produces 316L stainless steel propellers using the lost-wax investment casting process. The same method is used by leading global propeller manufacturers. We then CNC-machine the bore, keyway, and tapered hub to your exact shaft specification, and every propeller is statically balanced to ISO 484 Class S before dispatch.
Three blades remain the dominant configuration for outboard and sterndrive applications, giving the best balance of top-end speed, fuel efficiency, and reduced drag at planing speeds. 316L investment cast to your pitch-diameter combination, with hub bore, taper, and keyway machined to your engine's shaft specification.
A fourth blade reduces pitch-per-blade to achieve the same total thrust, lowering cavitation risk and reducing vibration on heavier-loaded or deeper-draft hulls. Preferred for pontoon boats, heavy cruisers, and loaded tenders where bow lift and smoothness at mid-range RPM matter more than peak top speed.
Shaft-drive propellers for inboard engines, twin-screw workboats, and custom watercraft require bore tapers, keyways, and blade geometries not found in any catalogue. Profab manufactures from your drawing or existing propeller sample, delivered balanced and ready to install.
The combinations below reflect the most commonly requested configurations. All can be modified — blade count, pitch, and bore are specified at enquiry. Dimensions outside this range are produced from drawing.
| Engine Power Range | Typical Diameter Range | Typical Pitch Range | Spline / Bore Options |
|---|---|---|---|
| 15–60 HP (Mid-Range) | 10"–12" (254–305 mm) | 9"–15" (228–381 mm) | 13-Spline (varies by engine — confirm at enquiry) |
| 60–200 HP (High-Power) | 13"–14.5" (330–368 mm) | 15"–21" (381–533 mm) | 15-Spline / Removable Hub Systems |
| 200–450+ HP & Sterndrive | 14.5"–16" (368–406 mm) | 17"–23"+ (431–584 mm) | Heavy-Duty 15-Spline / Solid Hub Options |
| Custom Commercial & Inboard | Up to 30" (up to 762 mm) | Customized per hull specs | Tapered Keyway Bore / Custom Spline |
The right combination of diameter and pitch determines whether your engine operates within its rated RPM range at full throttle. Running too high in pitch loads the engine short of its target RPM; too low and it over-revs. If you are replacing an existing propeller, send us the current prop markings — diameter × pitch are stamped on most hubs.
| Parameter | What to Check | Selection Advice |
|---|---|---|
| Current prop markings | Diameter × pitch stamped on the hub (e.g. 14 × 19) | Use as your baseline when replacing an existing propeller |
| Engine full-throttle RPM | Target within the engine's rated range | Too much pitch loads the engine short of target RPM; too little over-revs it |
| Shaft taper & bore diameter | e.g. 1:10 or 1:16 (SAE); bore measured at the large end | Confirm against your engine manufacturer's shaft spec before ordering |
| Keyway dimensions & rotation | Width × depth; RH or LH | Twin-screw installations need opposite rotation on each side |
| Blade count | 3 for speed, 4 for load and smoothness | Choose 4-blade for heavier, deeper-draft, or vibration-sensitive hulls |
Cast bronze is the other material family buyers weigh against stainless for a marine propeller. The right choice depends on which tradeoff — cost, castability, or corrosion behavior — matters most for your application. Profab casts propellers in 316L; the comparison below covers why, against the two bronze alloys most buyers are actually considering.
The 2–3% molybdenum content raises the Pitting Resistance Equivalent Number (PREN) to ≥ 24, and resistance comes from the alloy itself rather than a protective surface layer — unlike bronze, there's no patina to maintain. Lower cost to cast in small custom batches than either bronze alloy below, which is why Profab standardizes on 316L rather than offering bronze.
Grade 316L Profab StandardThe standard bronze choice for recreational and mid-size commercial propellers. Strong seawater corrosion and cavitation-erosion resistance, with tensile strength roughly comparable to hardened stainless — but it costs more than manganese bronze and is harder to cast and repair in small custom batches than 316L.
NAB / Nibral Not Offered by ProfabThe traditional lower-cost bronze option, easier to polish and repair than nickel-aluminum bronze. Its zinc content is a real liability: manganese bronze is genuinely susceptible to dezincification in saltwater, where zinc leaches out and leaves a porous, weakened blade surface over time.
Lower Cost Not Offered by ProfabAluminum is a separate comparison — the budget, sacrificial-failure alternative rather than a corrosion-focused choice. See Stainless Steel vs. Aluminum Propeller for that tradeoff.
Lost-wax investment casting builds the entire propeller as a single pour: hub, blades, and leading edges in one piece with no welds, no parting lines crossing blade surfaces, and no heat-affected zones. The ceramic shell process produces consistent wall thickness and internal grain structure throughout the blade. Post-cast CNC machining finishes the bore, shaft taper, and keyway to precise dimensions.
Blade surface finish is not purely cosmetic — it affects drag, corrosion resistance, and how the blade grips at speed. Profab offers two finish tiers depending on your priority.
Surface roughness on a propeller blade directly affects drag — the boundary layer separates earlier on a rough surface, increasing turbulence and fuel consumption. Profab polishes all blade surfaces to Ra ≤ 0.4 µm mirror standard, which also eliminates the surface micro-defects that initiate pitting corrosion in salt water. The standard choice for top-speed setups and long-term salt-spray resistance.
A lower-cost option that skips the final polishing pass. Some operators specify satin or as-cast surfaces on higher blade-count propellers (4 or more blades) for better surface grip, and it's a reasonable choice where top-end speed and salt-spray cosmetics matter less than unit cost.
Stainless steel propellers are specified where precision blade geometry, long service life, and consistent thrust output matter more than initial cost, whether on a performance sport boat or a working commercial vessel.
Resistance to blade deflection under high-torque acceleration improves the hole shot and keeps pitch geometry consistent at running speed. 3-blade 316L is standard from 80 hp upward.
Saildrive and shaft-drive propellers spend long periods fully submerged, demanding 316L as the minimum specification. Custom bore and shaft taper machining is essential, since no two saildrive configurations are identical.
The additional blade area of a 4-blade propeller distributes the higher torque of heavy-loaded hulls more evenly, reducing cavitation and stern vibration.
Commercial fishing vessels, pilot boats, and harbour tugs require shaft-drive propellers matched precisely to shaft dimensions for continuous high-load operation. Left-hand propellers for twin-screw applications are produced to the same specification as right-hand.
Boat manufacturers and OEM drivetrain assemblers often need a proprietary shaft taper or blade geometry not available in any catalogue. Profab produces OEM propellers in volume from approved drawings.
Aeration systems, water treatment mixers, and industrial waterjet applications drive fluid with impeller geometries operating continuously in corrosive water. 316L maintains geometric accuracy where bronze alternatives corrode unpredictably.
Every propeller is cast from certified 316L stock, so the molybdenum content that gives this grade its chloride resistance doesn't vary batch to batch the way it can with uncontrolled scrap-remelt material. The grade you specify is the grade you receive.
Catalogue propellers come bored to standard tapers (SAE 1:10 or 1:16). If you need a metric bore, an unusual taper ratio, or a specific bore-to-face perpendicularity, Profab machines bore and taper after casting, ensuring concentricity between the bore centerline and the pitch circle of the blades.
If you have an existing propeller that performs correctly, send it as a sample. If you have engineering drawings, send the CAD file. Profab reverse-engineers or works directly from documentation to produce a casting pattern that replicates the blade profile, pitch, rake, and cup geometry you specify.
Not seeing your question? Email us at [email protected] and we typically reply same day.
For high-speed outboard and sterndrive applications, we use computer-controlled dynamic balancing to simulate real-world operating conditions. For custom commercial inboard propellers, we inspect and certify geometric tolerances in accordance with ISO 484 Class S (Special) protocols.
ISO 484 is the international standard for marine propeller manufacturing accuracy and balance. Class S (Special) is the tightest classification, specifying maximum permissible blade pitch deviation, section thickness tolerances, and static balance limits. An unbalanced propeller creates a cyclic radial force on the shaft every revolution, which over time causes stern gland wear, shaft bearing failure, and hull vibration.
Yes — send your existing propeller as a physical sample, or provide engineering drawings, and Profab reproduces the blade profile, pitch, rake, and cup geometry from it. This is more reliable than approximating from a catalogue listing.
The diameter and pitch stamped on most hubs (e.g. 14 × 19), your engine's full-throttle RPM, shaft taper and bore diameter, keyway dimensions, rotation direction, and blade count. Send what you have and Profab can help confirm the rest.
Provide your required parameters, including propeller type, diameter, pitch, blade count, spline, stainless steel grade, and quantity.
We will work on the best solution based on your request and send you a specific quote within 24 hours.
30 days standard. Samples before full production run on new custom parts. QC report before shipment.
Sea, air, or express courier. Material certs and inspection report inside every box.
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Read More »If you already have the drawings, please send email to [email protected] directly for an instant quote.
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