Prop direction for 1995-2010 ski Nautique.

[Trojanbaseball22]

Hello Nautique community. What direction does the prop turn for 1995-2010 Ski Nautiques?

[Jonny Quest]

Correct Craft loves right-hand props.

[JayG80]

Your 2003 Ski Nautique will pull to the port (left ) as you reverse out of your boat slip. MasterCraft or Malibu will favor starboard.

[SilentSeven]

Correct Craft loves right-hand props.

Any idea why this is? Candidly, I wish they were lefties like my old Mastercraft. Two reasons I prefer left handed rotation.

First - when skiing with a driver only and no observer, the right handed prop torque pushes down the starboard side of the boat - the same side the diver sits on. This boat rides low on the sboard side and the sboard wake seems a bit bigger than the port wake. With a leftie, the weight of the driver offsets the torque of the prop for a more even ride.

Second - when reversing around docks, IMO its infinitely simpler to have the stern slide towards the starboard side as that's where the driver is. This makes it easy for the driver to single handedly land the boat as you slide the bow in, add a bit of reverse and watch the stern pull to the dock. Driver can reach out and grab the dock. My Mastercraft was so easy to dock, the Nautique not so much.

[msquito]

Any idea why this is?...

Curious as well. I'd always assumed that for wake boats like my 2000 SAN, particularly those of its *vintage, it had something to do with optimizing the shape/maximizing the pop for the normal heelside wake for wakeboarding. No data to back that assumption, but my goofy girls sure appreciate it when we surf (and even I tend to ride heelside because it's that much better).

[Jonny Quest]

Seven:

With a right-hand prop (viewed from the stern), the prop is spinning clockwise. That makes the opposite torque or "counter torque" trying to spin counter-clockwise. In other words, the R-H props help stabilize a boat with only a driver as the starboard is "lifted" up with the counter torque. The R-H prop does NOT push the starboard down...just the opposite. A L-H prop counter torque pushes the starboard side downwards and lifts the port side...just the opposite of the R-H prop. Correct Craft legend has it that the R-H prop configuration is safter and handles better. Before the 1.23:1 tranny that reversed the output shaft direction, most CC boats had reverse-rotation engines with 1:1 transmissions. This was to maintain the R-H prop shaft rotation. It would have been much easier to run L-H props with standard rotation engines with the 1:1 trannys -- just like MC, 'Bu, etc. Clearly, the CC experts wanted R-H prop shafts and propellers.

JQ

[SilentSeven]

Hey Jonny Quest ...thanks for the insights.

I'm still trying to visualize how a right handed prop lifts the starboard side...I guess I need to do a little more reading on torque vs counter torque. My butt-dyno-meter clearly has the starboard side of my boat depressed when there is no offsetting passenger. But I'll be the first to admit that observations vs what is actually happening are not always right.

Completely agree that CC did this deliberately and must have had a good reason to add the complexity.

Gonna have to poke around on this a bit I guess.

[Jonny Quest]

Seven:

As a kid, did you ever have a rubber-band powered propeller airplane made out of balsa wood? If you wind up the propeller, hold the airplane body and let the propeller go, the prop spins in one direction. If you wind up the prop and release your hold on the airplane while holding the prop, the body of the airplane will spin in the opposite direction of the prop. That is the effect of counter-torque. So, when the boat prop is spinning clockwise, the boat wants to "spin" counter-clockwise. Your car / truck works the same way. Open the hood of your car with the engine running. Most likely it will be spinning clockwise. Have a helper step on the throttle quickly and watch the engine. The engine will want to rotate counter-clockwise. That is effect of counter-torque. Same in the boat. R-H prop = counter torque attempting the "spin" the boat in a left-hand rotation.

JQ

[SilentSeven]

Okaaaay. So this is interesting.

GenAI (ChatGPT in this case) says counter-torque is involved but a full explanation requires consideration of a rotational moment generated around the longitudinal axis. Apparently, it's this rotational moment that lifts the right side and depresses the left side. ChatGPT offered to generate a diagram to better explain which I've requested but it's taking a while.

I'll paste in part of the ChatGPT discussion:

ChatCPT prompt from me. This is a follow-on prompt to clarify prior explanations.

provide an expanded explanation of the effects of how the torque reaction works addressing why the following statement is not accurate. If the propeller spins clockwise and the torque reaction is in the opposite direction, I would expect the right side of boat to lift, not the left side.

ChatGPT response

Great question—let’s clarify how torque reaction works in a boat and why the expectation in the statement is incorrect, despite being based on a reasonable interpretation of Newton’s Third Law.

---

❓ The Misunderstanding:

“If the propeller spins clockwise and the torque reaction is in the opposite direction, I would expect the right side of the boat to lift, not the left side.”

This statement assumes that the reaction torque would spin the boat in the opposite direction and that this would raise the starboard (right) side—but that interpretation oversimplifies how rotational torque is distributed in a real object like a boat.

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✅ Correct Understanding: Torque Reaction and Roll


When a right-handed propeller spins clockwise (as viewed from the stern looking forward), it applies torque to the water in that direction. By Newton’s Third Law, an equal and opposite torque is applied to the boat hull in the counterclockwise direction.

This reaction torque tries to roll the hull to port—that is:

• The port (left) side lifts
• The starboard (right) side dips

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Why the Left Side Lifts:


To understand this better, imagine holding a spinning propeller shaft in your hands:

• If the shaft spins clockwise, your hands would feel a counterclockwise twisting force.
• This force isn’t just a horizontal turning—it has a rotational moment around the longitudinal axis of the boat (the axis running bow to stern).

In a boat hull, this moment results in a rolling motion, not a flat spin. Boats are not free to rotate horizontally like helicopters; instead, they react with a roll—one side of the boat lifts while the other drops.

So, the counterclockwise torque (from the boat’s perspective looking forward) causes the boat to roll left, lifting the port side.

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✨ Visualization Analogy:


Imagine standing on a log in water and trying to spin a wheel clockwise in front of you:

• As you spin the wheel clockwise, your body (and the log) will tend to twist or roll the other way, which would make your left foot rise slightly and your right foot press down, if the log were wide enough to allow a roll.

---

Summary:

• A right-handed propeller spins clockwise when viewed from the stern looking forward.
• The reaction torque on the boat is counterclockwise (again, viewed from the stern).
• This reaction torque induces a roll in the boat—not just a twist.
• That roll lifts the port (left) side and lowers the starboard (right) side.
• The original statement misunderstands how torque manifests in the boat—it assumes a horizontal spin rather than a roll around the boat’s longitudinal axis.

While not totally grocking the physics here, this does suggest my observation that the right side of my 206 rides low on a RH prop is accurate.

[Jonny Quest]

It seems that Chat GPT is having a bad hair-day, and that the A.I. algorithm is acting a bit fickle today. Chat GPT just clarified:

✅ Clarification:

With a clockwise spinning propeller (i.e. a right-hand prop, as seen from the stern), the boat experiences a counterclockwise torque along its longitudinal axis (bow to stern).

---

Why?
The propeller spins clockwise (from the stern).

• Newton’s Third Law: the reaction torque on the boat is equal and opposite — so it's counterclockwise.

---

What this does to the boat:

This counterclockwise roll means:

• Port side (left) dips
• Starboard side (right) lifts

JQ

[SilentSeven]

ChatGPT can make mistakes. Check important info.

Not the first time I've see AI mistakes.

Those are physics that I can grock. Something else must be triggering what I'm observing.

What prompt did you use to get this clarified response?

[Jonny Quest]

What prompted the clarification was the quote you inserted from Chat GPT:

When a right-handed propeller spins clockwise (as viewed from the stern looking forward), it applies torque to the water in that direction. By Newton’s Third Law, an equal and opposite torque is applied to the boat hull in the counterclockwise direction.

This reaction torque tries to roll the hull to port—that is:

• The port (left) side lifts
• The starboard (right) side dips

When you read the Chat GPT response carefully, the first part is correct. However, there are contradictions in the next statement. Chat GPT stated that the torque is applied to the boat hull in the counterclockwise direction and then gets the "roll to port" piece backwards. If the hull wants to roll to port (counterclockwise), then the port side dips and the starboard side lifts. I called an engineer friend and verified. So then I asked Chat GPT to clarify, using specific phrasing, and got the response.

JQ

[SilentSeven]

I see now what you saw. Good catch!

By 'what prompt did you use'....I meant, what information did you put into ChatGPT to generate a the revised response? Forgive me if this is captain obvious stuff...when working with gen AI systems, the 'prompt' is the question you ask the system to answer. Question phrasing can matter as it impacts the answer the system will generate.

[Jonny Quest]

One of my not-so-good habits is reading things too darn fast. Apologies. I read "what prompted you to get a clarified response?" OK...now I understand your question: "what prompt did I give to Chat GPT to generate that response?" Well, I'm not at my home computer, so I will attempt to recreate my request / prompt to Chat GPT.

I asked: "a boat with a right hand propeller (when viewed from the stern), what direction does the hull want to spin on its longitudinal axis?" (or words to that effect)

I got a similar answer to the one you received. I then told Chat GPT that I thought the answer was only partly correct and asked for clarification. The message I posed is the Chat GPT response after I called out the mistake.

JQ

[Trojanbaseball22]

JQ and Silent Seven. Thanks for the discussion. I am getting quite the education about right and left hand prop and physics. JQ do you know if Nautique has always used RH prop rotation on the "Ski Nautique" from the beginning-1950's till a 2025 model year?

Also a 2021 GS20 has a LH rotating prop correct?