Boat Propeller Slip Calculator: Speed, Pitch and RPM Optimizer
The most complete free prop slip tool for US boaters. Solve for slip percentage, actual speed, required pitch, or target RPM. Get automated hull-type diagnosis, a pitch change advisor, WOT RPM compliance check, and a full PDF diagnostic report for any outboard, stern-drive, or inboard setup.
Select what to solve for, fill in the inputs, and hit Calculate to see your prop slip, diagnosis, and pitch recommendations.
| Pitch | Est. Actual Speed | Theoretical Speed | Est. WOT RPM |
|---|---|---|---|
| Run the calculator to see pitch options | |||
What Propeller Slip Is and Why It Costs American Boaters Speed and Fuel
Every boat owner has experienced the quiet frustration of checking their speedometer against a neighbor’s GPS and coming up short. You bought a 25-pitch propeller because the dealer said it would push your bass boat to 60 mph, but the GPS says 51 mph at wide-open throttle. That 9-mph gap is not a manufacturer lie. It is propeller slip, and understanding it is the difference between an expensive afternoon at the marina and a productive hour of diagnosis with the right numbers.
The Physics of Propeller Slip in Plain Language
A propeller pitch is the theoretical distance the prop would move forward through the water in one complete revolution if water were a solid and the prop could screw through it with zero slippage, the way a wood screw advances through lumber. A 21-inch pitch prop would, in theory, push a boat exactly 21 inches forward with every full rotation. In practice, water yields and the blades slip backward relative to the water mass they are pushing, covering less than the theoretical 21 inches of forward travel per revolution. That shortfall, expressed as a percentage of theoretical travel, is your prop slip.
Some slip is not just normal. It is physically necessary. If a propeller had zero slip, it would have zero blade angle of attack against the water, which means zero pressure differential across the blades, which means zero thrust. Mercury Marine, in their official prop slip documentation, explicitly states that slip is not a measure of propeller efficiency. It is a natural byproduct of how marine propulsion generates thrust. The question is not whether you have slip. The question is whether your slip percentage is appropriate for your hull type, engine, and propeller combination.
By the Numbers: According to the US Coast Guard 2024 Recreational Boating Statistics, approximately 11.9 million recreational vessels are registered in the United States. The National Marine Manufacturers Association (NMMA) reports that recreational boating contributes over $230 billion annually to the US economy. With millions of outboard-powered boats on American lakes, rivers, and coastal waters, propeller optimization represents a significant aggregate opportunity to improve fuel efficiency and reduce engine wear across the fleet.
The Standard Marine Formula
The formula used in this calculator is the same one published by Mercury Marine, Yamaha, and every credible marine engineering resource: Theoretical Speed in mph = (Prop Pitch in inches multiplied by Engine RPM) divided by (Gear Ratio multiplied by 1,056). The constant 1,056 comes from dividing 63,360 (the number of inches in a mile) by 60 (the number of minutes in an hour), converting the result from inches per minute to miles per hour. Propeller slip is then calculated as the difference between theoretical and actual speed, divided by theoretical speed, expressed as a percentage. This calculator solves for any one of five variables: slip percentage, actual speed, required pitch, required RPM, or theoretical speed, depending on which information you already have and which you need to find.
How This Five-Variable Boat Prop Slip Calculator Works
The five solve modes in this calculator address the full range of situations a boater encounters when evaluating propeller performance, from a simple first-time slip check to advanced prop selection for a new engine or a speed target for a tournament.
Mode 1: Calculate Slip Percentage
This is the baseline diagnostic mode. Enter your prop pitch (stamped on the hub in a format like 14 x 21, where 21 is the pitch), your measured WOT RPM from a tachometer, your gear ratio (found in your engine owner’s manual or on the engine spec sheet), and your actual GPS speed at wide-open throttle. Using GPS speed is strongly recommended. Boat speedometers and pitot-tube gauges are notoriously inaccurate, often reading 5 to 8 mph high or low depending on mounting position and tube condition. The calculator returns your slip percentage and cross-references it against the expected range for your selected hull type, giving you an immediate diagnostic: in range, slightly high, or excessive with specific causes to investigate.
Mode 2: Find Actual Speed from Slip Estimate
Useful when selecting a propeller before buying. If you know a typical slip percentage for your hull type (use the benchmark table below or the diagnosis from a previous prop), you can model what actual speed you can expect from a specific pitch at a given RPM before you spend money on a new propeller. This mode is particularly helpful for bass boat owners planning a prop upgrade who know their gear ratio, engine RPM ceiling, and hull slip history.
Mode 3: Find Required Pitch for a Target Speed
Enter your target GPS speed, planned WOT RPM, gear ratio, and expected slip, and the calculator returns the exact pitch you need to achieve that speed. This is the mode used by performance boaters dialing in a setup for tournament speed or fuel-optimal cruise. The pitch output is mathematically precise, and the Pitch Change Advisor table shows how nearby pitches within three inches of the calculated optimum would affect actual speed and WOT RPM.
Mode 4: Find Required RPM for a Target Speed
Given a specific pitch, gear ratio, and slip percentage, what WOT RPM do you need to achieve your target speed? This mode is useful for verifying whether a proposed pitch will push your engine toward or away from the manufacturer’s WOT RPM band. Enter your engine’s recommended WOT RPM range in the optional fields and the calculator checks whether the required RPM is within spec.
Mode 5: Theoretical Speed (Zero Slip Model)
Calculates the maximum possible speed your propeller could achieve if slip were eliminated, which is physically impossible but useful as an efficiency ceiling reference. Comparing your actual measured speed to the theoretical maximum tells you how far below perfect efficiency your setup is running and how much is theoretically recoverable through prop optimization.
WOT RPM Compliance Check
Most gasoline outboard engines are designed to operate at wide-open throttle within a specific RPM band, typically 5,000 to 6,000 RPM for recreational outboards, though this varies significantly by brand and model. Operating consistently below the lower limit strains the lower unit and may indicate the pitch is too high. Operating above the upper limit risks overrevving and accelerated wear. Enter your engine’s WOT RPM range from your owner’s manual and the calculator checks whether your current or proposed setup is in compliance, and if not, calculates exactly how many pitch inches you need to change to bring it within spec using the industry-standard 150 to 200 RPM per pitch inch adjustment rule.
Expected Propeller Slip Ranges by US Boat Type: Bass Boats to Offshore Rigs
No competitor in this space provides hull-specific slip benchmarks. The slip percentage that signals a problem on a tournament bass boat may be completely normal on a pontoon. Using a single 10-20 percent “normal” range for all boats, as most calculators do, leaves boaters with no context for their numbers. The ranges below come from published industry data from Mercury Marine, VIF Marine, and the marine propulsion research community, cross-referenced against real-world boater reports.
Bass Boat
Pontoon / Tri-Toon
Offshore / Center Console
Jon Boat / Flat Bottom
Ski / Wakeboat
Runabout / Family
Walleye / Troller
High Performance
Why Hull Type Determines Your Normal Slip Range
The slip range differences between hull types come down to three core factors: hull shape and drag, typical operating weight, and propeller design conventions. A bass boat hull is a deep-V planing design built to minimize drag once on plane and run efficiently at high speeds. Its propeller spends most of its time in a clean, relatively undisturbed flow behind a hull that is lifting out of the water. This low-drag, high-speed environment favors lower slip.
A pontoon boat is a fundamentally different situation. The flat-bottomed tubes create a large, drag-generating platform that pushes a substantial wall of water ahead of it even at full speed. The engine and propeller are working against much more resistance, which means more slip is necessary to generate the thrust needed to maintain speed. Expecting a pontoon to run at 12 percent slip like a bass boat is like expecting a semi-truck to run fuel-economy numbers like a sports car. They are different physics problems.
Three Real Boating Scenarios: Lake Erie, Florida Bay, and Lake of the Ozarks
Lake Erie, Ohio
Florida Bay, Keys
Lake of the Ozarks, Missouri
The Lake Erie walleye boat example shows a perfectly functioning setup. At 13.2 percent slip, the aluminum 21-pitch propeller is operating at the low end of the 15-22 percent walleye-troller benchmark, which is exactly where you want to be. The stainless upgrade option would likely bring slip down to 10-11 percent and recover 2 to 3 mph of top speed on those long runs between Erie ports and the offshore reefs, but the current setup is not broken.
The Florida Keys center console at 11.0 percent slip demonstrates the efficiency advantage of stainless steel propellers on offshore hulls. With a clean stainless 4-blade prop, the boat is near the lower end of the 8-14 percent offshore benchmark. Any attempt to push below 8 percent slip typically requires surface drive props or precision tuning work beyond the reach of standard recreational outboard setups. This is a well-dialed boat.
The Lake of the Ozarks pontoon at 26.1 percent demonstrates why hull-specific benchmarks matter. Taken in isolation, 26 percent slip sounds alarming. With context, it is almost perfectly normal for a heavy pontoon platform running a standard aluminum prop. If the owner switched to a 4-blade high-thrust pontoon-specific propeller, they might recover 2 to 4 mph and bring slip down to 21-23 percent, still within the normal pontoon range but noticeably faster on the water.
Six Expert Tips for Reducing Excessive Propeller Slip on US Recreational Boats
Use GPS for Your Speed Input, Not the Speedometer
The most common reason slip calculations return unexpected results is speedometer inaccuracy. Pitot-tube boat speedometers are notorious for reading high when the tube is mounted too high or is partially clogged, and low when fouled. A dedicated GPS unit or a GPS app on a waterproof phone gives you a true over-ground speed to the tenth of a mile per hour. Take three runs at WOT in the same direction and average them to account for any current effect on a river or tidal water. That GPS-averaged speed is the number to enter in the calculator.
Check Engine Height Before Changing Propellers
Engine transom height is one of the most underdiagnosed causes of high slip. An outboard mounted too low drags its anticavitation plate and lower unit through significant water resistance, which adds drag and increases slip by 3 to 8 percentage points without any prop change. An engine mounted too high lets air ingestion occur at the propeller (ventilation), causing the blades to spin in a mixture of air and water with dramatically reduced grip. The standard starting position is anticavitation plate flush with the boat bottom. If your slip is high and your prop is in good condition, adjusting engine height is a free diagnostic step before spending money on a new prop.
Switch to Stainless Steel to Recover 3-6% Slip
Aluminum propellers flex slightly under load, which reduces effective pitch in use compared to the stamped specification. A 21-pitch aluminum prop might behave more like a 19.5-pitch prop under WOT load, increasing slip. Stainless steel props are rigid and maintain their specified pitch, typically recovering 2 to 4 mph and reducing slip by 3 to 6 percentage points on the same hull. For aluminum-propped boats running at the high end of their slip range, switching to a matched stainless prop is the single highest-impact upgrade available without engine modifications. The cost is typically $300 to $700 for a quality stainless, versus $80 to $200 for a comparable aluminum.
Use the 150-200 RPM Per Pitch Inch Rule for Prop Changes
When the Pitch Change Advisor table shows you need to move pitch up or down to hit your WOT RPM target, the standard marine industry rule of thumb is that each inch of pitch change moves WOT RPM by approximately 150 to 200 RPM in the opposite direction. Reducing pitch by one inch raises WOT RPM by 150-200 RPM. Increasing pitch by one inch lowers WOT RPM by 150-200 RPM. This rule is approximate and varies by engine power, hull weight, and prop diameter, so any pitch change warrants a sea trial with a tachometer to confirm the actual RPM shift before making a permanent prop decision.
Inspect for Prop Damage Before Diagnosing Setup Issues
A bent blade, cupped trailing edge, or nicked leading edge can add 3 to 8 percentage points of slip compared to the same prop in perfect condition. Before spending any money on a new propeller or engine adjustments, pull your prop and inspect every blade face and edge carefully. Even minor dings on the leading edge create turbulence that reduces efficiency. A professional prop shop can recondition most aluminum props for $30 to $60 and stainless props for $50 to $100, often recovering most of the performance lost to impact damage. This is always the first diagnostic step when slip climbs unexpectedly on a previously well-running setup.
Test at a Consistent Load, Not Empty Boat vs Full
Propeller slip increases with load. A bass boat that runs 12 percent slip with one person and an empty livewell might run 17 percent slip with three anglers, full livewells, a cooler of ice, and a full fuel tank. If you are calculating slip to diagnose a performance problem, always run your measurements at a representative load, meaning the weight you typically carry when you feel the boat is underperforming. Comparing a loaded test result to an empty-boat benchmark creates a misleading diagnosis. The Pitch Change Advisor in this calculator uses your entered RPM and slip to model pitch options, so entering the loaded test data gives you prop recommendations that will work under real conditions, not just on an empty boat at the dock.
Quick Reference: Common Gear Ratios, Pitch Rules, and WOT RPM Ranges for US Outboards
The following reference data covers the most commonly encountered values for recreational outboard engines sold in the US market. Always verify your specific engine’s gear ratio and WOT RPM range in your owner’s manual, as these vary between model years and regional configurations.
| Gear Ratio | Common Engine Applications | Notes |
|---|---|---|
| 1.85:1 | Small outboards, 25-50hp class | Higher ratio = prop turns slower relative to engine |
| 2.00:1 | Various mid-range outboards | Common on many 4-stroke designs |
| 2.08:1 | Yamaha F115/F150, Mercury 90-150hp, most popular ratio | Most common recreational outboard gear ratio in US market |
| 2.17:1 | Mercury 150-200hp, some Evinrude | Slightly longer lower unit for deeper prop immersion |
| 2.29:1 | Various makes, some Suzuki | Check owner’s manual : often marked on lower unit plate |
| 2.33:1 | Mercury Verado 200-400hp, large Yamaha 225-350hp | Large outboard standard; check manufacturer spec sheet |
| 2.50:1 | Mercruiser I/O sterndrives, some inboard | Inboard/outboard applications run different prop diameter standards |
| Engine Type | Typical WOT RPM Range | Source / Notes |
|---|---|---|
| Standard recreational outboards (75-300hp) | 5,000-6,000 RPM | Manufacturer recommendation range, most common US outboards |
| Small outboards (25-60hp) | 5,000-5,500 RPM | Check owner’s manual for specific model |
| High-performance outboards (300-400hp+) | 5,500-6,200 RPM | Mercury Verado, Yamaha V8 : verify in owner’s manual |
| Mercruiser I/O sterndrive (GM 5.0/5.7L) | 4,200-4,800 RPM | Lower WOT range than outboards; different torque curve |
| Pontoon-specific 4-stroke (90-150hp) | 5,000-5,500 RPM | Pontoon loads typically shift WOT RPM toward lower end |
Frequently Asked Questions About Boat Propeller Slip
The standard marine formula for propeller slip starts with Theoretical Speed in mph = (Prop Pitch in inches times Engine RPM) divided by (Gear Ratio times 1,056). The constant 1,056 converts from inches per minute to miles per hour (63,360 inches per mile divided by 60 minutes per hour). Slip percentage = ((Theoretical Speed minus Actual GPS Speed) divided by Theoretical Speed) times 100. This formula is used by Mercury Marine, Yamaha, and every credible marine propulsion resource. Make sure to use GPS speed rather than your boat’s speedometer, as onboard speedometers are often 5-10 mph inaccurate.
Normal slip depends heavily on your hull type. Mercury Racing states that most setups fall in the 5-20 percent range. More specifically: bass boats and planing V-hulls typically run 10-18 percent slip. Offshore center consoles with stainless props run 8-14 percent. Pontoons and tri-toons normally run 20-30 percent, which sounds high but is completely expected for their heavy platform design. Jon boats and flat-bottom hulls typically run 20-28 percent. Using a single 10-20 percent benchmark for all boats is misleading. The hull-type benchmarks in this calculator give you context appropriate to your specific boat.
It depends entirely on what kind of boat you have. If you are running a pontoon boat with a standard aluminum propeller, 27 percent slip is normal and not a problem at all. If you are running a bass boat or offshore center console, 27 percent slip is significantly higher than the expected range and warrants investigation. Common causes in those high-performance hulls include prop damage or cupping, engine transom height too low creating drag, pitch too high for the engine’s torque curve, or excess boat weight. Enter your hull type in the calculator to get a specific diagnosis based on your slip percentage and boat category.
The industry-standard rule of thumb is that every one inch of propeller pitch change affects wide-open throttle RPM by approximately 150 to 200 RPM in the opposite direction. Reducing pitch by one inch increases WOT RPM by 150-200 RPM. Increasing pitch by one inch decreases WOT RPM by 150-200 RPM. This relationship is why staying within your engine’s recommended WOT RPM band is critical. An engine consistently running above its WOT RPM ceiling due to too-low pitch accelerates wear on pistons, bearings, and the powerhead. An engine consistently under-revving due to too-high pitch strains the lower unit gears and reduces combustion efficiency. The Pitch Change Advisor in this calculator uses this rule to show you estimated RPM for each pitch option.
Always use GPS speed. Pitot-tube boat speedometers are notoriously inaccurate for two reasons. First, the tube must be mounted at the correct position on the hull to read accurate dynamic pressure, and most factory mounting positions are compromised by hull shape. Second, partial tube blockage from sediment, vegetation, or aeration creates false readings that drift as boat speed changes. GPS provides true over-ground speed independent of any onboard sensor. For the most accurate slip calculation, run three passes at WOT in the same direction and average the GPS readings. If you are on moving water (river or tidal area), run one pass each direction and average to cancel out current effect. Nizpro Marine, one of the more respected prop tuning operations, specifically states they will only accept GPS speed for slip calculations, not speedometer readings.
Your engine’s gear ratio is in three possible places. First, check your owner’s manual under the specifications section. Second, look on the engine spec sticker on the engine itself, typically near the cowling or on the transom bracket. Third, search your engine model number on the manufacturer’s website (Mercury, Yamaha, Suzuki, Honda, Evinrude/BRP all publish full spec sheets online for every model year). The most common gear ratio in the US recreational outboard market is 2.08:1, used by many Yamaha and Mercury engines from 75 to 150 horsepower. If you cannot find your specific ratio and you have a standard recreational outboard in that horsepower range, 2.08:1 is a reasonable starting assumption that you can refine once you locate the actual spec.
Yes. The slip formula and the five solve modes work identically for stern-drive (I/O) and inboard engines. The only difference is the gear ratio value you enter. Mercruiser stern-drives commonly run a 1.84:1 or 2.0:1 gear ratio depending on the specific drive unit model. Older Volvo Penta and OMC Cobra drives have their own gear ratios, available in the service manual or on the drive unit data plate. Traditional inboard V-drive setups have varying gear ratios depending on the transmission model. The hull-type benchmarks are also applicable: a bowrider on a sterndrive is still a planning V-hull and should be compared against the runabout/family boat slip range, not the pontoon range.
Propeller ventilation occurs when air from above the water surface is drawn into the propeller’s working face, causing the blades to spin in a mixture of air and water rather than pure water. Air provides far less resistance than water, so the blades cannot generate meaningful thrust and the engine RPM climbs dramatically while speed drops. Ventilation produces extremely high slip readings (30-60 percent or more) and is usually audible as the engine suddenly revving without corresponding acceleration. The most common cause of chronic ventilation is engine transom height set too high, placing the propeller too close to the water surface. Other causes include cavitation plates that are damaged or missing, and hull designs with very shallow deadrise at the transom. If you see slip percentages that seem impossibly high (40 percent or more), ventilation is a likely cause rather than a prop selection problem.
Three-blade propellers are the standard for most recreational outboard applications. They provide the best combination of top speed and fuel efficiency for planing hulls in light to moderate loads. Four-blade propellers provide better hole shot (faster get-up-on-plane performance), reduced ventilation at high engine trim angles, smoother operation, and better performance under heavy loads, but typically sacrifice 2 to 4 mph of top speed at WOT compared to an equivalent three-blade at the same pitch. Pontoon boats benefit significantly from four-blade high-thrust designs. Wakeboats that need fast hole shots for getting skiers and wakeboarders up commonly run four-blade setups. Offshore performance boats and tournament bass rigs prioritize top speed and generally prefer three-blade stainless props. There is no universal right answer, but the slip calculator helps you evaluate what your current setup is achieving regardless of blade count.
Cavitation and ventilation are different phenomena that are often confused. Ventilation (described above) involves air being drawn into the propeller from the surface. Cavitation is a hydrodynamic process where water pressure around the propeller blade drops so low that water vaporizes locally, forming tiny bubbles. When those bubbles collapse, they create intense localized shockwaves that erode the propeller blade surface over time. True cavitation damage looks like pitting on the pressure face of the blades, often called “cauliflower” erosion. Cavitation is caused by blade design issues, too-high surface speed for the prop diameter, or running a badly bent blade. It is less common than ventilation on recreational boats but more damaging to the propeller over time. Both produce high slip readings, but the diagnostic and solution paths are different.
Propeller pitch is stamped on the prop hub in a format like 14.25 x 21 or 14 x 21, where the first number is diameter in inches and the second is pitch in inches. On some props, especially aluminum models, the marking may be molded into the hub surface rather than stamped, and can be hard to read if the hub is dirty or corroded. Clean the hub area with a wire brush and look for a two-number designation in that diameter x pitch format. If the markings are illegible, a marine propeller shop can often identify pitch using a pitch gauge that measures the actual blade angle. Mercury, Yamaha, and other manufacturers also maintain part number databases that list the specifications of their OEM props by part number, which is also typically stamped on the hub.
Negative slip means your actual measured speed is higher than the theoretical speed calculated from your pitch and RPM. In recreational applications, this almost always means your inputs are wrong, usually the gear ratio or tachometer reading. Mercury Racing specifically states that a negative slip result typically means the gear ratio is incorrect or the tachometer is not calibrated. In specialized applications, particularly surface-piercing props on high-performance race boats, props can achieve small amounts of negative slip through a phenomenon where the blade geometry generates extra thrust from supercavitation effects, but this is well outside normal recreational boating. If you get a negative slip reading, double-check your gear ratio against the manufacturer’s spec sheet before drawing any conclusions.
Yes. Every feature in this calculator, including the five solve modes, the hull-type diagnosis, the pitch change advisor, WOT RPM compliance check, PDF report download, and WhatsApp sharing, is completely free with no registration required. The tool is fully mobile-optimized and loads fast on standard cell signals. Download the PDF diagnostic report while you have connectivity and refer to it offline. The WhatsApp share button sends your results directly to your boat mechanic or marina contact without switching apps. All five calculators in the USCalculators Outdoors Hub are free and designed to work in the field, at the dock, and at the ramp.
Additional weight increases hull resistance and pushes the hull deeper in the water, which increases drag and requires more propeller thrust just to maintain the same speed. More thrust demand means more slip. A bass boat that runs 13 percent slip with one person might run 19 percent slip with three anglers, a full cooler, and 50 gallons of fuel on board. This load-related slip increase is why your boat always felt faster when you first bought it (probably tested empty by the dealer) versus how it performs on a fully loaded tournament or family trip. If you are selecting or evaluating a prop, always test at your typical operational load, not at the minimum possible weight, to get slip numbers that reflect real-world performance.
Run a slip calculation at the start of each season to establish a baseline, and any time you suspect performance has degraded. Comparing your current slip against your baseline from the same boat, same load, and same conditions tells you whether something has changed in your prop or engine. Common season-to-season changes that increase slip include minor prop blade damage from dock contact or underwater debris, marine growth on the hull in saltwater and brackish environments, engine performance degradation, and changes in typical load (a new bimini, a larger livewell setup, extra gear). Tracking your slip number over multiple seasons also helps you justify maintenance expenditures because you can quantify exactly how much speed you are losing to a worn or damaged prop.
The US Coast Guard (USCG) is the primary federal authority for recreational boating safety, including propeller-related incidents. Their annual Recreational Boating Statistics report, available at uscgboating.org, documents propeller strike incidents and safety recommendations. The USCG’s boating safety division publishes guidance on engine cutoff switch requirements and propeller guard regulations, which vary by state. The National Marine Manufacturers Association (NMMA) at nmma.org publishes industry standards that govern prop design and testing. State-level boating regulations, including speed limits, no-wake zones, and required safety equipment, are enforced by each state’s wildlife or natural resources agency.
Related Marine, Fishing, and Outdoor Calculators
These tools from the USCalculators Outdoors Hub and broader network are most often used alongside the Prop Slip Calculator by boaters, anglers, and outdoor enthusiasts.
Legal Disclaimer and Editorial Transparency
The Boat Propeller Slip Calculator is provided for informational and diagnostic purposes only. All speed and slip calculations are mathematical estimates based on the standard marine formula (Theoretical Speed = Pitch x RPM / (Gear Ratio x 1,056)) and are not a substitute for on-water sea trials with professional measuring equipment. Actual propeller performance varies based on hull condition, engine condition, water temperature, load distribution, sea state, and propeller wear. Hull-type slip benchmarks are sourced from VIF Marine, Mercury Marine, and industry research. Always verify your engine’s WOT RPM specifications and gear ratio in your owner’s manual before making propeller changes.
The pitch change advisor uses an industry rule-of-thumb of 150-200 RPM per pitch inch, which is an approximation that varies by engine, hull, and propeller design. Consult a qualified marine mechanic before purchasing or installing a new propeller. USCalculators.com operates independently and is not affiliated with Mercury Marine, Yamaha, NMMA, or any propeller manufacturer. External links are to official US government domains (uscgboating.org, nmma.org) or recognized marine industry sources. This page was last reviewed for accuracy in 2026.