Double screw on the outboard motor: when you need and how to choose the right one

Double screw (or counter-prop) for the outboard motor is not just a fashion accessory, but a serious technical solution that can radically change the behavior of the boat on the water. Many owners of outboard motors and stationary engines consider it a panacea for handling problems, but in fact it is not so clear. In some cases, the double screw really saves — for example, when a single screw can not cope with heavy load or the boat “scours” at high speeds. In others, it can worsen the dynamics or even damage the gearbox.

In this article, we will understand physics We compare it with the classic single propeller in 7 key parameters (from thrust to fuel consumption), and also give a step-by-step installation instructions - taking into account typical mistakes that even experienced boaters make. Compatibility with popular motors such as Yamaha F150 or Mercury 115The double screw is often the cause of disputes in forums.

If you've already encountered a boat that doesn't go well on planing, nose-to-nose or engine overheating at low speeds, maybe the problem is the propeller. But before buying a double, you should check 3 more critical parameters (we'll list them in the section on diagnostics).

How the double screw works: physics and advantages over single

The main difference between a double screw and a single one is that there are two bladed wheels that rotate in opposite directions. counter-prop) - compensates for the jet moment, which twists the boat in the direction opposite to the rotation of the propeller, this is especially noticeable on powerful engines (from 90 hp) and boats with a high freeboard.

Advantages of double screw:

• 🔹 Improved manageability The boat is less “leads” to the side, especially at turns and with sharp gas.
• 🔹 Faster access to planing due to the increased area of the blades (20-30% more than a single screw of the same diameter).
• 🔹 Decreasing vibrations The counter-screw extinguishes the turbulence that the front wheel creates.
• 🔹 Best traction at low revs - is relevant for trolling or towing skiers.

But there is a downside: the double screw. heavier (30-50% versus single), which increases the load on the gearbox, and it also requires more frequent balancing and can reduce the top speed by 5-10% due to increased water resistance. Suzuki DF140 double-rotor Solas Amita 3 Loss of speed will be ~8 km / h compared to the standard Aluminum 14×19.

Double and Single Rotor Comparison: A Key Parameter Table

To make an objective assessment of whether you need a dual screw, compare it to a single one in terms of basic performance, given for screws of the same diameter (14 inches) and pitch (19 inches) on a 115 hp engine:

Parameter	Single screw	Double screw.
Maximum speed	Higher than 5-10%	Lower 5-10%
Time to go out to plane	15-20% longer	Faster than 20 to 30 percent.
Managing cornering	Slogging propensity	Stable, less roll.
Fuel consumption	Lower 3-7%.	Higher 5-12%.
The gearbox load	Moderate.	Increased (risk of overheating)

From the table it is seen that the double screw loses in speed and economy, but wins in the acceleration and resilienceBest for:

• 🛥️ Boat with high freeboard (e.g., Barker 580 or Crimea 1753).
• 🎣 Fishing boats, where thrust at low speeds is important (trolling).
• 🏄‍♂️ Towing water skiers or wakeboarders.

⚠️ Attention: Powered motors less than 70 hp. The double screw is often not justified, because it puts an excessive load on the gearbox without a noticeable increase in handling, except for models with a reinforced gearbox (for example, the main gearbox). Honda BF100).

When a Double Rotor Is Really Needed: 5 Signs of Problems

Before buying a double screw, check if you have at least one of these symptoms:

1. Boat "scouring" at high speeds The motor pulls to the side, you have to steer constantly, which is a sign of an imbalance in the jet torque.
2. Long exit to glossing (more than 5 seconds at full load) Single screw does not create enough traction.
3. Vibration at the aft.Especially when accelerating, a single screw creates turbulence that the double rotor extinguishes.
4. The engine overheats at low speeds Single screw "slips", double gives a more uniform load.
5. It's hard to keep course in the wave The boat is cruising even with a trimmer.

If you have 2 of the things on your list, a double screw can help, but first rule out the other reasons:

Check the balance of the single screw (possibly bent blade)

Measure compression in the engine cylinders (low compression = power loss)

Make sure the trimmer is working correctly (unfixed trim impairs handling)

Check the boat load (overload = any screw will "slug")

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For example, if a boat Kazankah-5M motorized Mercury 90 It is not good for plane, the problem may not be in the screw, but in the misstep (too big) or gear-bearingThe double screw here only temporarily masks the problem.

How to choose a double screw: step, diameter and material

When choosing a double screw, consider 3 key parameters:

1. Diameter. - should be 1-2 inches less than a single one (for example, if it was 14×19, a double taker 13×17), this compensates for the increased area of the blades.
2. Step. - for heavy boats (weight > 800 kg), the step should be less by 1-2 inches, for light boats (up to 500 kg) - you can leave the same.
3. Materials:
   • 🔹 aluminum Cheap but fast wear (season 2) suitable for engines up to 60 hp
   • 🔹 Stainless steel More expensive, but stronger and more efficient (efficiency 10-15%), optimal for 90 hp
   • 🔹 Composite materials (for example, Solas Rubex) - light and resistant to corrosion, but rare on sale.

For popular engines there are ready-made solutions:

• 🛠️ Yamaha F150 — Michigan Wheel Apollo 4 (14.25×19, stainless steel).
• 🛠️ Mercury 115 — Turning Point Hustler 3 (13.5×17, aluminum).
• 🛠️ Honda BF100 — Solas Amita 3 (14×15, composite).

⚠️ Attention: On the engines Tohatsu some Parsun Double screws can conflict with the system Oil Injection Check the compatibility in the manual!

How to check the compatibility of the screw with the motor?

1. Find the engine data sheet section Propeller Selection.

2. check the maximum allowable diameter and pitch for your model.

3. make sure that the screw hub fits for an outboard motor shaft (e.g. Splined or Keyed).

4. check if a replacement is required propeller nut or thrust washer (often with a double-rotor package).

Step-by-step installation of double screw: instructions and typical errors

Installation of a double screw is not much different from a single one, but there are several critical nuances:

1. Remove the old screw:

   1. Turn off the motor (remove the ignition key).
   2. Relax the screw nut counterclockwise (use the end key).
   3. Remove the puck and the locking ring (if any).

2. Install a double screw.:

   1. Put it on the shaft. thrust washer (Combined)
   2. Install the front wheel of the screw (blades down).
   3. Put on a remote sleeve (importantly, without it, the counterprop will hit the gearbox).
   4. Install the rear wheel (counter-spin).
   5. Twistle the nut and lock it with a splint.

3. Check the balance. If you feel a beating, relax the nut and adjust the position of the blades.

Typical errors in installation:

• 🚫 Forget about it. sleeve - leads to blows of the counterprop against the body of the gearbox.
• 🚫 Pull the nut - deforms the hub, the screw begins to "beat".
• 🚫 Install the screw "upside down" - the blades should be directed downward (on most models)

Maintenance and repair: how to extend the life of a double screw

A double screw requires more care than a single screw. Here's a maintenance checklist:

Wash the screw with fresh water (especially after salt water)

Check the backlash on the shaft (let us assume no more than 0.5 mm)

Lubricate the nut carving molybdenum

Look at the slacks and the slacks.

Check the condition of the anode on the gearbox.

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The most frequent breakdowns and their causes:

Problem.	Reason.	Decision
High-speed vibration	Bent blade or imbalance	Balancing on the machine or replacement
Knocking at the gearbox	Wear of bearings from increased load	Replace oil in the gearbox (every 100 hours)
Maximum speed reduction	Wear of blade edges	Polishing or rotor replacement
Overheating of the engine	The wrong step (too big)	Reduce step by 1-2 inches

If the screw is damaged, you don't always have to buy a new one. aluminum screws can be restored with ferro-welding (Repair costs ~30% of the price of the new one) Stainless repair only by polishing - welding violates the structure of the metal.

TOP-5 double screws for popular outboard motors (2026)

Based on tests and feedback from owners, we have compiled a rating of the best dual screws for engines with a capacity of 90-150 hp:

1. Michigan Wheel Apollo 4 (14.25×19, stainless steel) - the best for high-speed boats, adds up to 3 km / h to the maximum speed compared to aluminum analogues.
2. Turning Point Hustler 3 (13.5×17, aluminum) - budget option for engines up to 115 hp, good for trolling.
3. Solas Amita 3 (14×15, composite) - lightweight and durable, but expensive (from 80,000 rubles.) Suitable for salt water.
4. Mercury Vengeance (14×19, stainless steel) - original screw for Mercury engines, ideal for towing.
5. Yamaha Performance (13.8×17, stainless steel) – optimized for Yamaha engines, reduces fuel consumption by 5–7%.

When choosing, focus on boat and style:

• 🏆 For race — Michigan Wheel Apollo 4 or Mercury Vengeance.
• 🎣 For fishing — Turning Point Hustler 3 (small step)
• 🌊 For saltwater — Solas Amita 3 (composite does not corrode).

FAQ: Frequent questions about double screws

Can I put a double screw on the 60 hp engine?

Technically, but not recommended - the gearbox of most 60-horsepower motors (for example, Tohatsu M60 or Parsun F60) not designed to be loaded, except for reinforced gearbox models (e.g. Honda BF60Before installation, check the maximum permissible weight of the screw in the manual.

Which screw is better: double aluminum or single stainless?

Depends on the task:

• 🔹 Double aluminum cheaper and better for traction at low revs (trolling, towing).
• 🔹 Single stainless It is more expensive, but gives +5-10% to the maximum speed and lasts longer.

For most boats, it is optimal. double-stainless It combines the advantages of both options.

Why did the engine become overheated after installing the double screw?

There are two reasons:

1. Too big. screw-step The engine is not gaining momentum, it's under load, and the solution is to reduce the pitch by 1-2 inches.
2. It's down. water-intake The double screw creates additional turbulence that can block the flow of water. impeller.

Should I change the oil in the gearbox after installing the double screw?

Yeah, necessarilyDouble screw increases the load on gear bearings, so:

• 🔹 Replace the butter with synthetic (for example, Mercury Premium Gear Lube).
• 🔹 Reduce the replacement interval from 100 to 50 hours.
• 🔹 Check the oil level every 10 hours of operation.

Can you balance a double screw yourself?

Balancing a double screw at home is possible, but requires accuracy:

1. Remove the screw and clean it of dirt.
2. Set it on balancer (Can be made from weights and bearings).
3. Scroll the screw - the heavier blade will fall down.
4. Remove the excess weight with a file or add a loader to the opposite blade.

For stainless screws, it is better to contact the workshop - an error in balancing will lead to vibrations and wear of the gearbox.