G23 Prop Fell Off .....

[scottb7]

Fits nicely...

[GMLIII]

Fits nicely...

Just curious how you attach the vintage 1980 trolling motor to your six figure G?

[Wayward]

Greggmck- good info, and great that you dug into it that thoroughly.......

I am not able to address a lot of it in depth right now, but I have a few quick points to make, because I don’t like to speak complete “nonsense”, as you said I did....

1- Take a look at all the sheared shafts...... as far as I have ever known, forged steel does not break cleanly like that. They create a much rougher break. I could be wrong about this, and I will leave that to the experts to comment. I also know that the shafts on my G had an obvious machined surface, whereas on an MC, it isn’t. I know I have tried to turn a forged shaft on a lathe before, and was not able to get a clean cut on it.... especially with the vibration you get on a shaft that length. Nonetheless, I am no expert. Maybe you can enlighten me further.....

2- A G is probably the most “bow down” surf boat ever built, so I’m having trouble believing that theory has much merit compared to the competition.

3- I have included a picture of my stock prop, and my alternate prop, from my MC. As you can see, it is an 18” prop, on a 1 1/8” splined shaft, on a boat that runs with the bow higher than a G while surfing. How is that for nonsense?!?!?

[2019 G21]

Greggmck,

Thanks for the info. My father is a PE also and I was explaining this shaft failure and he mentioned the same theory as you. He also felt that the fact that the shafts break just before the prop in all the pictures could also be a sign of prop cavitation either from prop actually pulling the oxygen out of the water under heavy load causing bubbles or even little air bubbles being introduced by the hull. He saidthe bubbles would be like hammers constantly banging the propeller. I guess similar in a way to detonation in an engine,and the constant knocking taking out pistons and such.

[Wayward]

Close up of hub....

[scottb7]

Just curious how you attach the vintage 1980 trolling motor to your six figure G?

Last owner after breaking shaft left the trolling motor in the boat. You simply hook onto swim platform, and hook up to one of the batteries. And home you go...Pretty cheap insurance to get you on your way...

So I just kept it in there. I figured if boat breaks down for any other reason (bad belt tensioner, etc.) I am covered. Pretty unlikely I would not have enough juice having two batteries...

[charlesml3]

Last owner after breaking shaft left the trolling motor in the boat. You simply hook onto swim platform, and hook up to one of the batteries. And home you go...Pretty cheap insurance to get you on your way...

So I just kept it in there. I figured if boat breaks down for any other reason (bad belt tensioner, etc.) I am covered. Pretty unlikely I would not have enough juice having two batteries...

Ha! ha! Have you tried this yet? How far do you think a trolling motor is going to push a 6000 pound boat on those batteries? I think someone stuck that trolling motor in there as a joke.

[greggmck]

Greggmck- good info, and great that you dug into it that thoroughly.......

I am not able to address a lot of it in depth right now, but I have a few quick points to make, because I don’t like to speak complete “nonsense”, as you said I did....

1- Take a look at all the sheared shafts...... as far as I have ever known, forged steel does not break cleanly like that. They create a much rougher break. I could be wrong about this, and I will leave that to the experts to comment. I also know that the shafts on my G had an obvious machined surface, whereas on an MC, it isn’t. I know I have tried to turn a forged shaft on a lathe before, and was not able to get a clean cut on it.... especially with the vibration you get on a shaft that length. Nonetheless, I am no expert. Maybe you can enlighten me further.....

2- A G is probably the most “bow down” surf boat ever built, so I’m having trouble believing that theory has much merit compared to the competition.

3- I have included a picture of my stock prop, and my alternate prop, from my MC. As you can see, it is an 18” prop, on a 1 1/8” splined shaft, on a boat that runs with the bow higher than a G while surfing. How is that for nonsense?!?!?

1) To learn more about forging check out this website: https://www.steelavailable.com/en/wh...steel-forging/ Furthermore, I don't know what you mean when you say "

shafts on my G had an obvious machined surface, whereas on an MC, it isn’t." as if this somehow indicates it is

forged. All shafts are machined at the prop end. Mastercraft uses a Splined shaft. By definition it is machined.

2) I don't know what measurements you have seen to state that the G is the most bow down boat ever built. All surf boats have a plate at the stern of the boat that can be used to rise the bow to create greater pressure at the stern resulting in a steeper wave with more push. This is the setting most frequently used to SURF. Skim boarders might prefer to lower the bow by lowering the plate to push the bow down. This reduces the pressure at the stern resulting in a longer and less steep wave. Every surf boat can raise or lower the bow based upon riding preference. Granted the G does have a lower gunwale in the bow. This is to improve driver visibility when in a bow high configuration. The down side of this design is that one can take on water over the bow when the ballast is full if you hit a large wave. Perhaps better visibility is attributed with a more bow down boat? But that is perception, not the angle of the hull to the water. Finally, the bow high attitude is ONE factor contributing to the failure. This factor combined with the 2:1 transmission, 17" prop, and fully loaded ballast at surf speeds ALL contribute to increase shaft loading. Many boats can have larger props, but not larger props with all of the other characteristics in a large enough sample size to experience the shaft shearing that has occurred. I believe we are talking about tens of shafts sheared in several thousand boats.

3). Stock prop on what? If you look at https://www.ozpropellers.com.au/mast...at-propellers/ The only Mastercrafts with 2:1 Gear ratios are the X20, X23. Both of these boats use the 16.0 or 16.5" props. Many boats use larger propellers than 17". But they don't have a 2:1 transmission, and push heavy surf loads too. I'm not defending this design, just identifying the factors that cause the failure.

[scottb7]

Ha! ha! Have you tried this yet? How far do you think a trolling motor is going to push a 6000 pound boat on those batteries? I think someone stuck that trolling motor in there as a joke.

Yeah, I tried it. Worked great. Not saying you get much speed. Trolling motors use very little power so can go a long time...Not saying you gonna get there fast. But better then having to have 3 guys lined up behind the platform kicking, I figured.

I think in actual use it would depend on wind, etc. how fast you would actually move but it works fine...very cheap insurance...

At first it bothered me to carry it, but after people had shafts break second time on same boat, I figured - since I had it - I better leave it in.

The issue I have is that we are first on the lake in March April and last off in October November. There is NO ONE that would be able to come save us on my baby sized lake.

[scottb7]

"Granted the G does have a lower gunwale in the bow. This is to improve driver visibility when in a bow high configuration. The down side of this design is that one can take on water over the bow when the ballast is full if you hit a large wave. Perhaps better visibility is attributed with a more bow down boat? But that is perception, not the angle of the hull to the water."

Yeah, NO...From the wakeboard perspective what is a fact, and I love about the G, is that it runs the least amount of bow rise - and yes I mean angle of the hull to the water - then most boats in general (and all nautiques in particular) to produce a comparable wake. And the gunwale is really high on the G, and is pretty darn difficult - thankfully - to take water over the bow. (Ease at which you can take water over the bow is the only thing I can fault my 2008 210. Absolutely everything else about that boat was unbelievable for its dry weight and ballasted weight.)

I would get an axis a22 or a24 in a heartbeat if my g didn't create the same wake with lower bowrise. But my wife would run into someone not being able to see...

[Wayward]

1) To learn more about forging check out this website: https://www.steelavailable.com/en/wh...steel-forging/ Furthermore, I don't know what you mean when you say "

shafts on my G had an obvious machined surface, whereas on an MC, it isn’t." as if this somehow indicates it is

forged. All shafts are machined at the prop end. Mastercraft uses a Splined shaft. By definition it is machined.

2) I don't know what measurements you have seen to state that the G is the most bow down boat ever built. All surf boats have a plate at the stern of the boat that can be used to rise the bow to create greater pressure at the stern resulting in a steeper wave with more push. This is the setting most frequently used to SURF. Skim boarders might prefer to lower the bow by lowering the plate to push the bow down. This reduces the pressure at the stern resulting in a longer and less steep wave. Every surf boat can raise or lower the bow based upon riding preference. Granted the G does have a lower gunwale in the bow. This is to improve driver visibility when in a bow high configuration. The down side of this design is that one can take on water over the bow when the ballast is full if you hit a large wave. Perhaps better visibility is attributed with a more bow down boat? But that is perception, not the angle of the hull to the water. Finally, the bow high attitude is ONE factor contributing to the failure. This factor combined with the 2:1 transmission, 17" prop, and fully loaded ballast at surf speeds ALL contribute to increase shaft loading. Many boats can have larger props, but not larger props with all of the other characteristics in a large enough sample size to experience the shaft shearing that has occurred. I believe we are talking about tens of shafts sheared in several thousand boats.

3). Stock prop on what? If you look at https://www.ozpropellers.com.au/mast...at-propellers/ The only Mastercrafts with 2:1 Gear ratios are the X20, X23. Both of these boats use the 16.0 or 16.5" props. Many boats use larger propellers than 17". But they don't have a 2:1 transmission, and push heavy surf loads too. I'm not defending this design, just identifying the factors that cause the failure.

1- AFAIK, and by looking at the splines themselves, the shaft splines are rolled......

2- No measurements, just easy observations. While surfing, the G series boats run with a much lower bow attitude than any other competitive wakeboat. In most regards, this is one of the best aspects of the G while surfing. It is a well known attribute, and owners love that they can see better while driving. I don't understand what you mean about having lower gunwales in the bow. As far as i can remember, my Gs had fairly uniform gunwale heights from the back to the front. The thing I remember most, is how much bow rise the boat didn't have while surfing, and I liked that. Have you ever driven a Malibu MXZ while surfing, and without a 1000lb bow bag in it? That would give you an idea of a boat that rides bow high while surfing. And they run a 2:1 with a 17" prop....... and there are plenty of those out there for a good sample group.

3-New XStar (with any motor), and the X26 with a 7.4l, run a 18" prop with a 2:1 gearbox.

Have a chat with the service manager at a few different dealers....... the failure rate is more like 50% which makes sense, when at least half of the G owners on PN have had failures, and several have had multiple failures. I know members on here that have had failures, that didn't bother posting about it....

either way, I'm not trying to bash anything. They all have their own stupid issues, and their own engineering fails. This has gotten old, though. This problem is now 5 years old, and still happening at a high occurance rate. Something needs to be done IMO.

[Evening Shade]

I know it will never happen, but it would be cool to see a stress test on prop shafts from Nautique, MC, Bu, and Tige to see how much torque each can withstand before they fail.

[Wake.BC]

I’ve heard of one Tige failure and it was on a older boar, no Malibu failures... so yeah there must be something different here.

You can’t go by saying it’s the angle of the boat when surfing, they’re all the same. They all run 17” props on the 2:1. Prop angle too steep on Nautique?


Sent from my iPhone using PLT Nautique

[Wake.BC]

I’ve heard of one Tige failure and it was on a older boar, no Malibu failures... so yeah there must be something different here.

You can’t go by saying it’s the angle of the boat when surfing, they’re all the same. They all run 17” props on the 2:1. Prop angle too steep on Nautique?


Sent from my iPhone using PLT Nautique

[Bevostein]

I wonder if Nautique should move to splined shafts vs a keyway.

From this article - http://gearsolutions.com/features/inside-splines/

The benefits of using a splined shaft in the place of a keyed shaft are many. The spline connection provides an equally distributed load along the sides of the teeth. This shared load provides a longer fatigue life verses a keyway drive. Different types of spline tooth forms allow for stronger drives, the ability to slide, transfer of rotational concentricity, allowance for misalignment and, in the case of helical spline drives, the transfer of axial and rotary motion at the same time.