G23 Prop Fell Off .....

[DanielC]

Here is some thoughts on the propeller shaft problem.
First of all, the propeller on an inboard, or V-drive boat runs a an angle to the direction of water flowing past it, because water basically follows the bottom of the boat, and this causes one side of the propeller, the side with the blade going down to have more thrust, than the side of the propeller going up. A right hand propeller had the descending blade on the right side of the boat,and the higher thrust on the right side of the boat, so the boat tends to move left. This unbalanced thrust also bends the propeller shaft slightly. Not much, but a little.
Now obviously, as the propeller shaft rotates the shaft is constantly bring bent, on one side only. The shaft is flexing, and relaxing, like a spring.

Steel and it's alloys have a physical characteristic called a fatigue limit. Bend a piece of steel less than the fatigue limit, and you can bend it an unlimited number of times, without failure. Bend it more than the fatigue limit, far enough, or often enough, and it breaks.

Now, lets get back to the propeller shaft, specifically on on a G-boat. Use the boat for surfing, and you operate the boat significantly bow high, as compared to a faster cruising speed. Add in the surf tabs, and you may also cause the boat to travel slightly sideways, or "crabbed". If describing the boat like an airplane, the nose is pitched up, and the nose of the boat is yawed to one side. This type of operation probably increases the angularity of the propeller to the water flow going past the propeller. This increases the unequal thrust on the propeller, and the shaft. Add in a lower gear ratio, and a larger diameter propeller, and 550 HP engines, to better the performance of the boat, and I could see how the increased stresses could actually approach the fatigue limit of the propeller shaft.

So why did Correft Craft not catch this problem until the boats have been sold and used for a while? I suspect Correft Craft did not test the boats for a long period of time, with heavy (overloaded, beyond stated capacity) loads. There could also be some metallurgical issues in some propeller shafts. Heat treating alloys of steel can increase it's strength, but it requires very accurate temperature control, and times at temperature. Very possible there was a problem there.

A simple solution, in my opinion, the "G" boats need a larger diameter propeller shaft.

[scottb7]

What could nautique have said? I will easily answer that. Start with an apology. "We messed up. We apologize. We are trying to not erode your trust in the brand. You can call your dealer within x miles and we will send them out to retrieve you if you verify your propeller has f'n fallen off".

How about something like that. Not rocket science.

You suggest an across the board recall to switch shafts. But guess what THEY HAVEN'T DONE THAT. They have yet to do a DARN THING! Am I wrong? What have the done? They have said they are looking into it. That is it. They said they have made production changes... WHAT have they done for current owners!!!!!!!!!!!!!!!!!

[scottb7]

http://abcnews.go.com/Business/top-n...ry?id=19092158


http://www.forbes.com/sites/katelee/...orate-apology/

"We are extremely sorry for the frustration this has caused our customers and we are doing everything we can to make Maps better," Cook wrote in the letter.

http://www.perfectapology.com/corporate-apologies.html

[TX-Foilhead]

http://www.youtube.com/watch?v=YgUKPNk2blo

Theses guys broke a shaft, they're a little rougher on theirs than you are and I do t remember hearing them complain even though they obviously did a little more damage to their boat. They fixed it and moved on and everyone is chasing them this year.

[ffmedic74]

Only thing is that the G23 shouldn't sink. Great video.

[wakerider107]

What could nautique have said? I will easily answer that. Start with an apology. "We messed up. We apologize. We are trying to not erode your trust in the brand. You can call your dealer within x miles and we will send them out to retrieve you if you verify your propeller has f'n fallen off".

How about something like that. Not rocket science.

You suggest an across the board recall to switch shafts. But guess what THEY HAVEN'T DONE THAT. They have yet to do a DARN THING! Am I wrong? What have the done? They have said they are looking into it. That is it. They said they have made production changes... WHAT have they done for current owners!!!!!!!!!!!!!!!!!

It's a work in progress, man. Relax. Nautique will do the right thing.
Also, I'm sure if you were to call your local dealer, they will come tow you in. However that is not Nautiques decision to make.

[scottb7]

I am relaxed. Thanks for your concern about me. Why do you say it is not Nautiques decision to make? Nautique could pay the dealer to tow the boat owners in. Just like mfgs pay dealers for factory recall work.

[Ryan1776]

Laptom-It won't be Nautique that will test them. They most likely don't do that type of testing. They'll have the supplier test them. Unless it's like myself and Daniel mentioned, if it's a metallurgical problem, another lab, or the steel supplier will have to figure it out.

Daniel-Excellent point about the ascending and descending blades. That P-factor would certainly exacerbate the issue! And to go a littler further, the gyroscopic procession would cause that extra thrust-load-to occur 90° in the direction of rotation, so as that crack propagates those variable forces have to wreak havoc on that shaft.
You're dead nuts on the heat treating too. If the molecules of the steel don't realign themselves correctly you get an occlusion. Basically a gap in the structure of the steel. That makes a microscopic stress riser.
So many things could be going on!

But I still don't think they need a larger diameter shaft.
Here's how I got there.
Take for example my buddies race car. Approx 700ft/lb torque. Torque converter multiplies tq applied approx 2.0:1. 1st gear ratio of 2.5:1 Final drive ratio of 4.10:1 over two axles.
700x2x2.5x4.10/2= 7,175 ft/lbs per axle WHEN the car hooks with zero tire slip. Keep in mind that is a perfect situation and there are a other variables. But my point is this, those axles are 1.400" Yes, they are bigger but considering amount of torque applied is much higher than a boat, and considering a prop in water will not hook up like a tire on a sticky drag strip, I don't think the prop shaft size is to blame.
What's the ratio of the transmission/ V-drive? Isn't it something like 1.48:1?? So lets say it makes 550 ft/lbs. 550x1.48=814 ft/lbs applied. Not even close. It all comes down to using the right material and/or heat treating process.

Scott-I totally agree with the apology. It would have been easy. But my 2010 Grand Cherokee had a recall, last month, the transfer case would shift into neutral while it was parked, away from the vehicle and it could roll away. I didn't get an apology, I got a letter in the mail saying, bring it to the dealer and will fit you in in two weeks, sit there for 45min while they reflash the ECU. Ok whatever. But this car has been on the road for 4 years and I just got the recall. There has to be enough instances of a runaway Jeep for them to issue a recall not to mention narrowing down which ones to recall. At least if your prop shaft brakes, you're there to take some control of the situation! My example about a complete recall was really just a rebuttal for the trolling motor, I know you were joking. But here is why the can't do it....yet.
Lets say they recall and swap every prop shaft from every G series since its inception. Ok. Problem is without root causing the issue, those shaft maybe bad as well. So now you THINK you have a fixed problem and you go out and it breaks, now you'll really be pissed off because your perception will be, "they can't make a simple prop shaft! This is two prop shafts that were bad on my boat!" When in reality, your original prop shaft could have been in a lot that was fine. There is a method to all this.
But I will say again, an apology would have been a nice thing for sure.
And I totally agree with you, if a customer has an issue like that Nautique could/would probably already has issued a statement that if a dealer has to recover a G series boat that they will reimburse the dealer for costs associated.

[lucky7t]

G23 Drive Shaft Issues?

I agree with you about the shaft diameter but your not including length. If it's longer than a car then it needs to be a larger diameter IMO

Is it possible it's torsion stretching? (If that's a word) in other words could its length allow it to twist?

[Ryan1776]

Lucky-Good call! And you're exactly right. I did think about that part, just forgot to write it out, the reason I forgot is because as I was pondering this I guessed the length where close enough to each other. The axle overall is about 60", so in half 30" take off length for the differential and I was guessing maybe 20" +/-... I don't know the length of a G series but my boat is 18" I think. So if anything, its better (shorter) on a boat than on a car.
Yes, absolutely torsional displacement would increase as the shaft gets longer, at the same load. Would it get longer? Probably not in the lengths and materials where talking about. In order for the shaft to lengthen it would have to twist to a point where it would become "plastic" and deform and create a taper somewhere along the length of the shaft.
As far as a "stretching" radially? Sure. How much? I have no idea. I don't know the material, the treating process, the length. And to be honest I probably don't have the math aptitude to calculate that out! lol But you can't calculate that at the overall length either. You'd have to know the length from the "inboard" side of the keyway at the prop and same at the flange from the trans/v drive assembly.

[ffmedic74]

I don't believe boat manufacturers are required to keep logs similar to what car dealers/manufacturers do that is centralized to identify broken items/patterns. If this were required, then you would have a much better tracking system.

[nyryan2001]

X80, X55, X35, X45, X46, Xstar, ASR, MXZ24, etc etc etc.

all heavy comparable boats that folks slam with 4-6k additional ballast and go bonkers with 400-550 hp.

No snapped shafts with these boats ^^^. And they are on the thinner 1 1/8" shafts!

Its not like the Gs are going into unchartered territory as it pertains to power and weight. These other boats are there and their shafts arent snapping.

[Ryan1776]

ffmedic74-While they may not be required to track those things, I can just about guarantee they do. I work for a small company and we track everything. But as I said, even with a tracking system, what lot number went on to what machines, you sometimes just have to rely on the manufacture of that particular part to determine which lot was bad. And that won't happen overnight.

[scottb7]

Mount this bad boy to your swim platform and your good to go.

I believe there is a certain irony that the description for this unit says the following "Indestructible composite shaft backed by a lifetime warranty."

http://www.amazon.com/Minn-Kota-Fres...5359202&sr=1-1

[Ryan1776]

Scott-I couldn't find the adapter to connect that to Perfect Pass....
Gonna have to fab one up!