Props for Watersports: Best Setup for Towing Skiers

After 20 years working on outboards, I've propped hundreds of tow boats. Most people get it wrong because they chase top speed instead of focusing on what actually matters: getting skiers out of the water fast and holding consistent speed under load.

Propeller Pitch: The Most Critical Spec

Pitch is the distance a prop would travel forward in one complete rotation if it were moving through a solid. It's measured in inches—a 17p prop theoretically moves 17 inches per revolution.

Higher pitch (19-21 inches) acts like overdrive. Your boat will hit higher top speeds but needs more power to spin up. If your engine can't reach its rated WOT RPM range—usually 5,000-6,000 RPM for most outboards—you're over-propped. The engine lugs, acceleration suffers, and you'll struggle pulling heavy skiers.

Lower pitch (13-17 inches) gives you the grunt needed for towing. The prop spins easier, producing more low-end torque. You sacrifice 2-3 mph at the top end, but skiers pop out of the water cleanly, and the boat holds speed better when they're carving hard. For towing, I typically recommend pitches 2-4 inches lower than what you'd run for cruising.

According to propeller experts, changing pitch by 1 inch typically shifts engine RPM by about 150-200 RPM. If you're currently hitting 4,800 RPM at WOT and your engine's rated for 5,400 RPM, dropping 2 inches of pitch should put you in the sweet spot.

Three-Blade vs Four-Blade: What Actually Matters for Towing

The blade count debate comes down to what you're doing on the water.

Three-blade props have less surface area in the water, creating less drag. They're efficient at higher speeds and work well for slalom skiing where you need 25-36 mph consistently. Top speed is higher, fuel economy is slightly better, but holeshot—that initial punch to get on plane—is weaker. If you're running a lighter boat or pulling experienced skiers who get up easily, three-blades work fine.

Four-blade props add surface area, which means more grip. Acceleration is noticeably faster, handling is sharper at low speeds, and they excel at getting loaded boats on plane. When you've got a 200-pound skier in the water, ballast in the hull, and four people on board, that extra blade makes a measurable difference. You'll lose 1-2 mph at the top end compared to a three-blade of the same pitch, but for recreational towing and wake sports, it's the better setup.

Ruben Rhodes at Reliable Marine, one of the top Suzuki dealers in the country, notes that modern four-blade props with larger 16-inch diameters now deliver holeshot performance that rivals traditional three-blade advantages, making them even more versatile for mixed-use applications.

Propeller Diameter and Clearance

Diameter is the circle made by the blade tips as the prop spins. It's measured across from one blade tip to the opposite tip.

Larger diameters move more water per revolution, generating more thrust at lower speeds. For slower towing activities like tubing or getting beginners up, a larger diameter helps. But diameter is limited by your hull and drive unit clearance—you need at least 10-15% of the prop diameter as gap between the blade tips and the hull to avoid cavitation and vibration.

Smaller diameters spin faster with less resistance, which works for lightweight, high-speed applications. For slalom skiing where you need sustained speed rather than brute pulling power, a moderate diameter (14-15 inches on most outboards) is the target.

Before buying a larger diameter prop, physically measure the space between your current prop tips and the hull. If you don't have at least 1.5 inches of clearance, going bigger will cause problems.

Cupping: The Detail That Improves Grip

Cupping is a small curve or lip rolled into the trailing edge of each blade. It's not on every prop, but when it's there, it makes a difference.

The cup helps the blade hold water instead of slipping, which reduces ventilation—that's when air gets sucked down to the prop and you lose thrust. Cupped props deliver measurably better acceleration, hold RPM more consistently under load, and can add 200-300 RPM to your WOT reading compared to an uncupped prop of the same pitch.

For towing, cupping helps when skiers are cutting hard and loading the engine. The prop maintains bite instead of breaking loose. You'll also see slight top-speed gains—usually 1-2 mph—because slip is reduced.

Matching Props to Engine RPM Range

Every outboard has a rated WOT RPM range stamped in the owner's manual. For most modern four-strokes, it's 5,000-6,000 RPM. Two-strokes often run higher, around 5,500-6,500 RPM. Your prop choice must allow the engine to hit this range at full throttle with a normal load.

If your engine over-revs—hitting 6,200 RPM when it's rated for 5,800 RPM max—you're under-propped. The prop pitch is too low, and the engine is screaming. You'll burn extra fuel, risk overheating, and accelerate internal wear. Add 2 inches of pitch to bring RPM down.

If your engine under-revs—topping out at 4,600 RPM when it should hit 5,400 RPM—you're over-propped. The engine is lugging, can't breathe properly, and you're leaving power on the table. Carbon buildup increases, and you risk fouling plugs or overheating because the cooling system relies on RPM to circulate water efficiently. Drop 2 inches of pitch to let the engine spin freely.

Ruben Rhodes explains his diagnostic process: "The motor has an RPM range that you need to meet. The first thing I do is make sure the engine height's correct… then I look at my RPM." Engine height affects how water flows to the prop, which directly impacts RPM and performance. If the cavitation plate is too high above the hull bottom, you'll ventilate. Too low, and you create excessive drag.

Real-World Setup: 175 HP Outboard for Towing

Let's walk through a typical scenario. You've got a 21-foot bowrider with a 175 HP four-stroke outboard. The engine's WOT range is 5,100-5,600 RPM. The boat came with a stock 14-inch diameter, 19-inch pitch, three-blade aluminum prop.

Baseline test: With two skiers, a driver, and an observer on board, you run the boat at WOT and check the tach. It reads 4,750 RPM. The boat feels sluggish getting on plane, and pulling a 230-pound skier takes multiple attempts.

Wrong fix: You think more pitch equals more speed, so you try a 21-inch pitch prop. Now the engine struggles even harder, topping out at 4,500 RPM. Acceleration is worse, and skiers complain about weak pull.

Correct solution: You need more low-end torque. You switch to a 14-inch diameter, 15-inch pitch, four-blade stainless steel prop. At WOT with the same load, the engine now hits 5,350 RPM—right in the middle of the target range. The boat planes in half the time, skiers get up on the first pull, and the setup holds speed better when they're cutting aggressively. You've lost about 2 mph of top speed (now 38 mph instead of 40 mph), but towing performance is night-and-day better.

This scenario plays out constantly. People chase the wrong numbers and end up frustrated. The prop that makes your boat fastest empty isn't the prop that tows best loaded.

Stainless Steel vs Aluminum: Material Matters

Aluminum props are cheaper—$150-250 versus $350-500+ for stainless. But aluminum flexes under load. When you're pulling hard, the blades flatten out slightly, effectively reducing pitch and losing efficiency. Aluminum also dings and bends easily if you hit a rock or stump.

Stainless steel props are stiffer, so they maintain blade shape under load. They deliver better grip, more consistent thrust, and handle impacts better. Ruben Rhodes is blunt about material choice: "We don't even stock aluminum props. We do everything stainless steel. The only guys that would want to run aluminum are rental boat guys or guys that run really skinny water."

For serious towing, stainless is worth the investment. The performance gain is measurable, and the prop will outlast two or three aluminum replacements.

Props for Specific Watersports

Different activities have different demands.

Slalom skiing requires sustained speeds of 25-36 mph for experienced skiers, depending on the course and skier weight. You need a prop that holds speed cleanly without hunting or surging. A three-blade stainless prop in the 17-19 inch pitch range works well if your engine can spin it to the upper end of its RPM range. The flatter, cleaner wake from a three-blade setup is also preferable for slalom.

Wakeboarding and tubing demand strong acceleration and pull. Four-blade props with lower pitch—typically 13-15 inches—are ideal. Riders need that instant punch to get up, and the boat has to hold speed even when they're loading it hard during tricks or when pulling multiple tubes. For boats carrying ballast to build a bigger wake, you'll often need to drop another 2 inches of pitch to compensate for the added weight.

Two-ski beginners need slower, steady pull—around 16-20 mph. A four-blade with moderate pitch (15-17 inches) gives smooth, controllable power without ripping beginners off their feet.

Gear Ratio and Drive Height Considerations

Your engine's gear ratio—usually stamped on the lower unit or listed in the manual—affects how pitch translates to performance. Common ratios are 1.75:1, 2.0:1, or 2.33:1 on outboards. A higher ratio (like 2.33:1) multiplies torque, so you can run a higher-pitch prop and still achieve target RPM. A lower ratio (1.75:1) needs a lower-pitch prop to hit the same RPM range.

If you don't know your gear ratio, you can't accurately predict how a prop change will affect RPM. It's stamped on the lower unit near the prop shaft or listed in your engine manual.

Drive height—the vertical position of the motor on the transom—also matters. If the cavitation plate sits more than 1 inch above the hull bottom, you'll likely ventilate, especially during sharp turns or holeshot. If it's buried too deep, you add drag and lose speed. The general rule is to set the cavitation plate level with the hull bottom, then adjust up or down based on performance. For more on how to optimize engine height and angle, see our guide on engine mount height and angle.

Spun Hub: A Common Towing Failure

Propeller hubs use a rubber insert to absorb shock and protect the drive shaft. Under high torque—like pulling a heavy skier—that rubber can spin inside the prop, separating from the hub. When this happens, the engine revs normally, but the boat barely moves. RPM climbs, but speed doesn't.

To diagnose a spun hub, mark a line across the hub and prop barrel with a grease pencil, then run the boat hard. If the line separates, the hub has spun. The only fix is a new hub insert or a new prop. This is more common with aluminum props and cheaper aftermarket hubs. Quality stainless props with pressed or bonded hubs are far more resistant to spinning. For more info on this issue and other common prop problems, see outboard goes into gear but won’t move troubleshooting tips.

Altitude and Operating Conditions

If you boat above 3,000 feet elevation, your engine loses about 3% of its power per 1,000 feet due to thinner air. At 5,000 feet, you're down roughly 15% compared to sea level. This means you'll need a lower-pitch prop to hit the same WOT RPM you'd achieve at sea level.

Water conditions also matter. Saltwater is denser than freshwater, so a prop that works in the Great Lakes might over-rev slightly in the ocean. Rough water or heavy chop increases load on the prop, effectively acting like a higher pitch. If you're boating in variable conditions, aim for the middle of your engine's RPM range rather than the top to maintain headroom.

Propeller Maintenance and Damage Prevention

Props take abuse. Fishing line wraps around the shaft and scores the seal. Rocks chip blades. Debris dings the leading edges.

Check your prop every few trips. Pull it off and inspect the hub—look for rubber dust or cracks in the insert. Run your finger along each blade's leading edge to feel for dings or bends. Even a small ding disrupts water flow, reducing efficiency and causing vibration.

If a blade is bent, don't try to hammer it straight unless you've got proper tooling. Improper straightening weakens the metal and throws the prop out of balance, which damages seals and bearings in the lower unit. For stainless props, a shop can usually repair minor damage. Aluminum is cheaper to replace than repair.

Keep the prop shaft and splines greased. Every time you pull the prop, clean old grease off and apply fresh marine-grade grease. This prevents corrosion and makes future removal easier. We recommend checking best marine greases and lubes for your outboard to keep your equipment running smoothly.

Vent Plugs and Exhaust Systems

Some lower units have vent plugs or exhaust relief holes drilled into the gearcase. These allow exhaust gas to aerate the prop during holeshot, reducing load on the engine and helping it spin up faster. This is particularly useful on high-performance two-strokes, where instant throttle response matters.

Four-strokes generally don't benefit as much from vent systems since they produce less exhaust pressure, but some aftermarket props incorporate vent holes in the blade barrel for similar effect. If your prop has vent holes, don't plug them—they're there for a reason.

Buying the Right Prop: What to Tell the Shop

When you call a prop shop or place an order, have this information ready:

• Engine make, model, horsepower, and year
• Current prop specs (diameter, pitch, blade count, material)
• Current WOT RPM with a normal load
• Boat length, weight, and typical passenger load
• Gear ratio (stamped on lower unit or in manual)
• Primary use (slalom, wakeboard, tubing, cruising)
• GPS top speed with current setup

Without this data, any recommendation is a guess. The more specific you are, the better the advice you'll get.

For quality props, look at brands like Michigan Wheel, Solas, Turning Point, PowerTech, or OEM options from Mercury, Yamaha, or Suzuki. Avoid no-name imports—they use inconsistent pitch specs, soft metals, and unreliable hubs. You'll end up replacing them within a season. For more guidance on choosing OEM vs aftermarket parts, see OEM vs. Aftermarket Outboard Parts: What’s the Difference?.

When comparing OEM to aftermarket, understand that some non-OEM manufacturers produce high-quality parts using the same factories and materials as OEM suppliers. The key is choosing established aftermarket suppliers with proven track records rather than generic discount parts.

Watersports Safety and Prop Awareness

U.S. Coast Guard statistics show 145 propeller strike accidents in 2023, resulting in 23 deaths and 133 injuries. Most of these happen during skier retrieval.

Never restart your engine after a skier falls until you've visually confirmed the skier is clear of the stern and the tow rope is not in the water near the prop. Approach fallen skiers at idle speed only, and keep them in sight at all times. Circle wide so the rope doesn't drift toward the prop.

Federal law requires a dedicated observer on board—someone other than the driver watching the skier. The observer's job is to communicate hand signals from the skier to the driver and to keep eyes on the skier if they fall. Most states also require a wide-angle rearview mirror if you don't have an observer.

Check your prop hub weekly for fishing line. Even a few wraps create friction, overheat the hub, and can cause the rubber to separate. After every day of towing, pull the prop and clear any debris from the shaft.

Sources:

• https://boatingmag.com/features/2012/03/13/prop-talk-maximize-your-boats-potential/
• https://www.youtube.com/watch?v=1Q4OgpxnUR4
• https://www.barts.com/blogs/news/how-to-pick-the-right-propeller-for-your-boat
• https://boatingmag.com/tips-for-using-your-boat-for-tow-sports/
• https://www.wakemakers.com/blogs/resources/wakemakers-basic-prop-guide
• https://www.boatus.com/expert-advice/expert-advice-archive/2013/april/which-prop-is-right-for-your-boat
• https://uscgboating.org/statistics/accident_statistics.aspx
• https://www.boat-ed.com/blog/is-water-skiing-dangerous/
• https://boattests101.com/united-states/boating-resources/other-water-activities/water-skiing,-towed-devices-and-water-sports
• https://jlmmarine.com/

After each towing session, flush your engine with fresh water for at least 10 minutes using muffs or a built-in flush port. This prevents salt and mineral deposits from building up in the cooling passages, which keeps your thermostat from seizing and your water pump impeller from running dry. For detailed maintenance, check out our outboard water pump replacement guide.