Broken prop shaft
Printed From: CorrectCraftFan.com
Category: General Correct Craft Discussion
Forum Name: General Discussion
Forum Discription: Anything Correct Craft
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=41427
Printed Date: October-05-2024 at 12:22am
Topic: Broken prop shaft
Posted By: 81nautique
Subject: Broken prop shaft
Date Posted: July-05-2017 at 8:16pm
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So the Hurricane continues to win these little battles by cutting another day short this weekend. After running really well the weekend before at Quinners party we felt comfortable enough to take it to the river and put some hours on it. Everyone that drove or rode in the boat that weekend commented on how smooth it was. We ran about 20 miles up river, did some socializing then turned around to head back. About half way I dropped into idle to ride out some big rollers and when I dropped it back in gear it gave a big clunk. I knew it was broke good so I just opened the hatch to make sure we weren't sinking. Prop shaft snapped right at the coupler. Luckily it was busy and a couple of guys on a pontoon went out of their way to tow us about a mile to the nearest launch and then even gave me a ride to retrieve our trailer at our put in site which was still about 6 miles away. Looking at the shaft it appears there has been a fracture there for a while so this is probably an issue that started a while ago and finally gave up. Question is why does an ARE shaft with probably 100 hours on it break. I've been meticulous with alignment on this boat, checking it probably more times than I have ever done on all my other boats combined. There's never been any change every time I checked. At lunch to day I stopped by the machine shop and had them press the broken stub out of the coupler. There's evidence there that the taper never really seated very well into the coupler which was custom made by ARE to fit the Hemi. I confess I never did lap the coupler end of the shaft so I guess had I been more attentive I may have been able to avoid this if that's really why it broke. Here's some photos, if anyone has anything to add I'd appreciate any advice. New shaft is already on it's way, summer is too short.  left side is real dark and apparently been cracked for a while, also the dark center spot looks like it migrated from the keyway. but again why? out of alignment?, don't think so. Was the shaft never seated properly in the coupler and moving around a bit, I'll tell you we had to put the coupler in a press to get the stub out so it certainly seated partially.  The dark area is the beginning of the taper  You can see where the narrow part of the taper is seated well and the wider part is not. So anyway we made it back to safety with the help of some good samaritans but I would sure like to know what happened so I can learn from it. Installation error, bad taper fit, is the motor possibly moving under load, sure doesn't appear to be. One thing I have never done is check the alignment with the boat sitting in the water, it's always been on the trailer. Worth a look once I get it back together. |
Replies:
Posted By: TRBenj
Date Posted: July-05-2017 at 8:26pm
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Damn that's a ball buster. If the coupler wasn't seated fully on the taper, could you have been aligning to a coupler face that wasn't perpendicular to the shaft? (Can't see the pics btw). |
Posted By: 81nautique
Date Posted: July-05-2017 at 8:30pm
that's one of my theories Tim. |
TRBenj wrote:Posted By: Donald80SN
Date Posted: July-05-2017 at 9:38pm
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Alan, I am not an Engineer nor did I sleep in a Holiday Inn Express last night, but maybe just faulty shaft material? Just a bad batch of steel the shaft was made from? A lot of metal comes from overseas now. Sad, but true. Just a theory. Donald ------------- 1980 Ski Nautique SOLD Back to Cypress Gardens 2002 Sport Nautique, GT-40, FCT2, Cover Sports, Tower Bimini, Inc., Wet Sounds Audio System, Star Gazer Wake Edition S. 1968 Ski Nautique, Project. |
Posted By: jimsport93
Date Posted: July-05-2017 at 9:46pm
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Sorry to hear that Alan. Glad you made it in safe. And on top of the water. Really enjoyed one of your last videos (FB.....I think). She was sure running strong and looking great. She will be back! ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=2798 - 93 Sport Nautique |
Posted By: SNobsessed
Date Posted: July-05-2017 at 10:31pm
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Alan - I would contact ARE & see if they would do a metalurgical lab analyisis. If there is any material or manufacturing issue, I am sure they would want to know about it. ------------- “Beer is proof that God loves us and wants us to be happy.” Ben Franklin |
Posted By: 8122pbrainard
Date Posted: July-05-2017 at 10:36pm
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Alan, I agree with Tim's theory regarding alignment to the face of the coupling and if the shaft wasn't seated fully then there sure would have been a very slight out of parallel shaft. On the ARE's I've installed, I have lapped them and did find that the tapers between the coupling and shaft were off. The other issue is the taper is very short and steep so it's harder to fully seat. Keep moving forward. One of these days I'll get a ride! ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: 81nautique
Date Posted: July-06-2017 at 9:18am
| Well sorry about the pictures, I didn't realize Photobucket no longer allowed third party hosting without a fee. I'll have to find a new host, the sad part is every photo I've ever hosted (like the Hurricane thread) with them is also now a dead link. I can see new photos being subject to this but to block previously allowed photos is sort of a d*ck move. |
Posted By: 81nautique
Date Posted: July-06-2017 at 9:27am
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So after some thought I'm going to lap the new shaft to the coupler and then put it on some blocks and check the coupler face runout before installing it. I'll have it machined if need be. Realign it and then check it again with the boat in the water and see where it is. Pete, to your comment, I was told yesterday that ARE did change the taper of the coupler end on their newer shafts. he didn't say why, only that it was an improvement. I had to stay with the old taper because the coupler was custom made to the old taper spec and I'd have to pull the mating piece off the transmission and send it to them again and I don't want to loose the time and money it cost for a new one. I'll get it lined up perfect and take my chances. It should be fine if I make sure it's trued up correctly. |
Posted By: JoeinNY
Date Posted: July-06-2017 at 10:37am
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After breaking a few of them ARE’s –that I had custom ordered from the strongest shaft material they could get, always at the coupler, always starting at the really deep keyway I have given up on them. That taper is short, and that keyway is deep. Lapping it will help, getting it square after that will also help, but if it happens again general propeller will likely make you a dual taper shaft with a longer shallower taper on the coupling side and a better key system. It wasn’t cheap but it was cheaper than the ARE – The 3 broken ARE shafts and 3 bent up 1492 Acme’s off my 83 - are about the ugliest waste of 3500 bucks I have had in my long storied history of throwing money into boats. Might be a good project for Duane in Indy. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: 81nautique
Date Posted: July-06-2017 at 10:48am
I agree the keyway seems far too deep and is exactly where mine broke. I'd hate to think it couldn't handle a sub 300 hp motor but the fact that they have changed their taper means something. I wonder if the keyway has changed as well. If it wasn't July I would take more time and go a different route. I'm probably setting myself up for another hit, Guess I'll look into general prop over the winter. |
Posted By: Hollywood
Date Posted: July-06-2017 at 11:58am
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If you're rotating the shaft during your alignment then you'd find the coupler face is not square. The keyway on the new Elbert's coupler is long and square (1/4"?) just like the prop end. |
Posted By: JoeinNY
Date Posted: July-06-2017 at 12:30pm
Well that makes sense, glad they could learn from my field test results over the last 5 years. Do they put a pin in the key to keep it from sliding like General Propeller? ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: 8122pbrainard
Date Posted: July-06-2017 at 12:34pm
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With them adding a key and keyway, they obviously don't trust their skills at making tapers and it showed when I've lapped in their tapers!! There shouldn't be any key!! ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: 63 Skier
Date Posted: July-06-2017 at 1:01pm
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Pete, if they sold those shafts without a key people would be spinning them in the taper more often than not. I'd guess that 1 in 20 of their customers would take the time to lap the shaft into the taper, maybe less. I think it's just practical for inboard shafts to have a key, but some engineering has to be put into the taper and key design, as it sounds like Joe indicated to one of the suppliers. ------------- '63 American Skier - '98 Sport Nautique |
Posted By: 8122pbrainard
Date Posted: July-06-2017 at 1:07pm
I sure feel a proper fitting taper would help the 19 of the 20? Then, if not, I'd say 19 of those customers should not be installing their own shafts!  ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: phatsat67
Date Posted: July-06-2017 at 1:21pm
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Dang Alan, that sucks. I guess I was too hard on the throttle at Quinners. (thanks for letting me run it around again). Joe is the shaft expert. Kev has had Duane in indy make some pretty neat stuff all around. Would be a great option if something else breaks. Do you have a good shop locally that could machine lap the coupler than face it after it was installed on the shaft? I've always wondered how far off the coupler faces are. I try and do my alignment by moving the shaft into all 4 possible positions once my initial alignment is set to check coupler face and shaft runout. Hopefully this doesn't break. We have put about 200 hours on my brothers ARE in the 89. Extra 1.23 torque and slightly less HP than the Hemi. |
Posted By: Duane in Indy
Date Posted: July-06-2017 at 1:27pm
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FWIW, Kevins prop shaft/coupler assy measured with in .001 square after assembling. I cut the taper on the shaft. When I blued it up I could see no reason to lap it You could drop it onto the shaft and the coupling would lock up without any extra effort. He supplied the shaft and coupling; and I provided the machine work. ------------- Keep it as original as YOU want it 1978 Mustang (modified) |
Posted By: 63 Skier
Date Posted: July-06-2017 at 1:29pm
I've never thought about it that way, but really would make sense. When you add up the cost of a shaft, lost time, and possible cost of a prop, it would be good insurance against alignment issues. ------------- '63 American Skier - '98 Sport Nautique |
Posted By: 81nautique
Date Posted: July-06-2017 at 6:54pm
I do the same Zach and didn't measure any discrepancies. That doesn't mean it stayed that way though if the shaft didn't seat properly. probably my bad for not being more diligent with checking the fit. Measuring from the depth of the keyway that leaves the shaft less than .750" . there's a lot of material hogged out of there. I'll be meeting Duane at lake James next week so I think I'll bring the new and broken parts with so we can have a beer and think it through. If we decide I'd be better off sending the new shaft back for the later revised version so be it. I want to get the boat back together asap and it might cost me a few extra weeks to have a new coupler machined but would be worth it in the end. |
Posted By: MrMcD
Date Posted: July-06-2017 at 7:26pm
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I installed a new ARE shaft, now has 50 hours on it but this thread has me concerned. I know I lapped the prop well but do not remember lapping the coupler end. Maybe time to tackle that job? Mine was installed in 2014 is that the new or old version? Sorry about your troubles but thanks for pointing out an issue to be addressed! Mark ------------- |
Posted By: Hollywood
Date Posted: July-06-2017 at 7:38pm
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I had a woodruff key in a boat I took apart 5 years ago. The coupler I got this year from Elbert's had a square key. No pin Joe. |
Posted By: Riley
Date Posted: July-06-2017 at 8:52pm
Me too. We've got about 50 hours on ours. I'd be pretty disappointed if it broke. If I remember right, they required the nut be torqued to 60 lbs? |
Posted By: MrMcD
Date Posted: July-06-2017 at 10:22pm
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They learned years ago that square corners make weak spots in machined parts. Engine Crankshafts have rounded corners or fillets as they call them. This really increased the strength of crankshafts when they figured that out. Even Pistons have slightly rounded corners behind the piston ring grooves. Maybe the ARE folks just did not have that experience. We learn something every day. ------------- |
Posted By: MechGaT
Date Posted: July-07-2017 at 12:06am
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As I am sure several know, but some may not, the ripples indicate crack growth. The closer ones point to where it started and the ones farther apart indicate where it was speeding up due to the reduced cross section. The big chunk in the middle is where it finally broke. We have known for some time that sharp corners are bad, but surprisingly they still get left. That was my first thought. ------------- '92 Sport Nautique |
Posted By: phatsat67
Date Posted: July-07-2017 at 12:30am
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Alan, I think the beers next weekend will help get it figured out. Let's solve some world problems as well. See you Saturday am. HW. I will pack brackets for Duane. |
Posted By: tryathlete
Date Posted: July-07-2017 at 12:48am
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As a ranking ameteur who never even aligned a prop shaft, let alone replace one with an ARE, but who does have some mechanical aptitude, is there a reason why splines aren't used in conjunction with the taper instead of a keyway? Square corners are bad enough but reduction in cross-section to 7/8" seems to point to using a larger shaft diameter if the keyway is going to stay. I know that's impractical at this point. Splines sure don't fail like that keyway. They're more expensive to machine but there must be another reason that I'm missing |
Posted By: Duane in Indy
Date Posted: July-07-2017 at 7:36am
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Yes splines are expensive to cut. You get one company making shafts and another making couplings and they don't match up perfectly. No way to correct splined setups either. Also 1 failure per several thousand doesn't warrant change. Get a donor shaft and machine it to fit. Cheap easy fix. Or see if you can get any warranty help from the original maker. I like the "Beer Engineered" method listed earlier. Now if we could just get Pete down to interject his thoughts next week.  ------------- Keep it as original as YOU want it 1978 Mustang (modified) |
Posted By: tryathlete
Date Posted: July-07-2017 at 10:21am
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I used to be in the steering wheel business. We sold steering wheels that fit onto splines and tapered steering column shafts with a hub mated to the wheel with Huck fasteners. Never had issues with fit. Doesn't Mastercraft use splines/taper on their propellor to shaft engagement? |
Posted By: KENO
Date Posted: July-07-2017 at 12:09pm
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A Mastercraft splined propshaft. Picture courtesy of Ebay Straight splines, no puller required. Just like the 6 bazillion outboards of all sizes floating around out there. 
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Posted By: 81nautique
Date Posted: July-07-2017 at 12:15pm
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Not to beat this to death but I stumbled onto the patent info, regarding the coupler taper it appears the steep taper was deliberate to facilitate "easy" removal and decrease man hours required. From the patent application "A coupling receives a steeply tapered end of a propellor shaft and is secured thereto with a lock nut held in place with a set screw. A housing taper is steeper than known locking tapers to facilitate housing removal. The housing is internally threaded to receive an extractor element which, after lock nut removal, is screwed into the housing for abutment with the end of the propellor shaft with continued advancement of the extractor element resulting in housing separation from the shaft." http://www.freepatentsonline.com/5306093.html" rel="nofollow - full link |
Posted By: Riley
Date Posted: July-07-2017 at 12:21pm
| Just curious, is everyone that has bought one of these using a torque wrench to lock the shaft into the taper? Does that matter? |
Posted By: phatsat67
Date Posted: July-07-2017 at 12:45pm
| Ken, is that coupler side splined too? MC has used splines for propellers for a while now. |
Posted By: tryathlete
Date Posted: July-07-2017 at 1:00pm
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Splines on both ends seems like a winner to me. There must be some logical reason why the keyway is used instead of splines. From wiki Splines are ridges or teeth on a drive shaft that mesh with grooves in a mating piece and transfer torque to it, maintaining the angular correspondence between them. ... An alternative to splines is a keyway and key, though splines provide a longer fatigue life. |
Posted By: Duane in Indy
Date Posted: July-07-2017 at 1:16pm
More than likely a 10" crescent and a piece of pipe ------------- Keep it as original as YOU want it 1978 Mustang (modified) |
Posted By: 8122pbrainard
Date Posted: July-07-2017 at 7:03pm
And please, anti seize on the nut threads. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: KENO
Date Posted: July-07-2017 at 8:20pm
The ones I've seen had splines on both ends, but I don't know if they all are |
Posted By: Duane in Indy
Date Posted: July-07-2017 at 8:55pm
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Don't forget-----use a brass nut ------------- Keep it as original as YOU want it 1978 Mustang (modified) |