Broken prop shaft!
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Boat Maintenance
Forum Discription: Discuss maintenance of your Correct Craft
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=48774
Printed Date: November-15-2024 at 1:21am
Topic: Broken prop shaft!
Posted By: Briandarflinger
Subject: Broken prop shaft!
Date Posted: June-01-2020 at 1:06pm
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Hello everyone. I have a 87 ski centurio n that I just rebuilt from the ground up. First day out, everything s working great. As I'm about to pull the boat out of the water, I put her in reverse, and pop!, Driveshaft breaks clean right at the coupler. Anyone ever hear of this happening? What could be the cause? Thanks in advance |
Replies:
Posted By: juniorwoody
Date Posted: June-01-2020 at 1:10pm
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Poor alignment most likely I think. ------------- The value of money spent on new adventure far exceeds the value of money saved for the future |
Posted By: Jonny Quest
Date Posted: June-01-2020 at 1:12pm
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Unfortunately drive shafts can and do break. Poor alignment is the culprit in many failures. Make it easy on yourself and replace with a dual-taper shaft. A.R.E. And General Propeller in FL are good options. JQ ------------- Current 2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
Posted By: 8122pbrainard
Date Posted: June-01-2020 at 1:32pm
Absolutely agree. ------------- /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 < |
juniorwoody wrote:Posted By: Briandarflinger
Date Posted: June-01-2020 at 3:24pm
| Not very confident feeler guage illignment is a accurate way.. too many variables. Both shaft and trans couplers have to be100% perfect for that to be any good. |
Posted By: Briandarflinger
Date Posted: June-01-2020 at 3:28pm
| Both couplers have to be dead. Not a .01 of wobble, and both faces must be absolutely perfect. Correct me if I'm wrong |
Posted By: 8122pbrainard
Date Posted: June-01-2020 at 3:30pm
Brian, The feeler gauge method has worked for many years and still does but you are correct that the couplings need to be faced to the bore. Any better method? There's not enough shaft to bolts on a laser alignment tool. Tell us about your results with the feeler gauge. ------------- /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: Briandarflinger
Date Posted: June-01-2020 at 5:19pm
| Thanks for the response. I did align with a feeler gauge last time, and I THOUGHT it was good. But,as I said, as I did it, it seemed like it was arbitrary. My new shaft is on its way, . I'll give it another try!. Just for curiosity sake, I'm going to try and do it mathematically,,just to see if there's anything I obvious. |
Posted By: TRBenj
Date Posted: June-01-2020 at 5:35pm
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If you think the alignment was “arbitrary” then I suspect you may have gotten caught up in the details and missed the big picture. Forrest through the trees, as they say. Maybe one of our resident ME’s can comment how one might align with “math” instead of measurement. |
Posted By: 8122pbrainard
Date Posted: June-01-2020 at 5:40pm
I'd sure like to know how too.  ------------- /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: MourningWood
Date Posted: June-01-2020 at 6:47pm
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One the shaft, is (was) there any 'blueish' color around where the shaft packing? I've seen a shaft overheat and break there because the packing was too tight. Butch Stevens of Inboard Specialties (San Jose, Ca) taught me how to do alignment. (decades ago). He convinced me that the best way to do it was in the water, although not very practical all the time. ------------- 1964 Dunphy X-55 "One 'N Dun" 'I measured twice, cut three times, and it's still too short!" |
Posted By: MrMcD
Date Posted: June-01-2020 at 7:28pm
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You can verify your couplers are pretty darn straight by using the technique of adjusting the gap to as close to zero as possible and then rotating the prop shaft and double checking. Your gap should be the same before and after rotating the prop shaft 180*. Far as I know this is the industry standard and you do not need to revisit the technique. It works, if yours broke something was wrong with the shaft or your alignment. Hope the repair goes well. As mentioned early in this post, the tapered shafts save a lot of time on install and if you ever need to repair and are nearly the exact same cost as a standard shaft. ------------- |
Posted By: 8122pbrainard
Date Posted: June-01-2020 at 8:57pm
Brian, Did you purchase a single or double taper shaft? If single, are you also getting the coupling? Keep in mind the coupling to a straight shaft fit is an interference fit so the coupling is typically bored to match the tolerance of the shaft. ------------- /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: GottaSki
Date Posted: June-01-2020 at 9:32pm
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Pete could align an engine under .001" with a stick of gum on a cold enough day, i think you're going to learn something on this project ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: 8122pbrainard
Date Posted: June-01-2020 at 9:58pm
 Brian, Don't believe a word To says!! Seriously, I've fought alignments just like everyone has. They can be frustrating to say the least. You think you have it and then one small adjustment throws everting off. A couple things to remember and the key one is understanding the basics of what alignment is and what the goal is. Then always remember alignment starts at the strut and then goes forward. Keep us informed on what your progress is and ask if you have any questions. ------------- /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: briandarf
Date Posted: June-01-2020 at 10:23pm
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Thanks guys.! now that I'm home on my laptop, instead of my phone, I can elaborate..I have a 47-3/4" x1" double taper shaft. I very carefully checked the alignment with my feeler gauge. My thinking is: there's AT LEAST 4 things using the feeler guage wont tell you. #1 is the trans coupler true to axis?- if not, no measurements are valid- and how would you know? 2. is the shaft coupler perfectly aligned to its axis? AKA 'wobble" 3 Was my old shaft perfectly straight? " 4- are both mating faces PERFECTLY clean.- or feeler guages dont work Id bet its rare not to have at least one of these issues. No? ------------- darf |
Posted By: 8122pbrainard
Date Posted: June-01-2020 at 10:28pm
1,2 and 3 4 clean the faces first.
------------- /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: briandarf
Date Posted: June-01-2020 at 10:40pm
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Dont take this I'm being argumentative-I just think of why things might not work constantly.. - I remember spinning the couplers while I was installing the shaft- thinking both couplers could be off axis equally and mated together,but as long as the engine and shaft are in alignment it wouldnt matter and could have been fine since manufacture.. couplers could wobble together and everything be just fine,, and then when you try and rotate them 180 you could get a big difference and massively out of whack .. I know I'm going down a rabbit hole for no reason,, but I'm just sayin = you cant try to be VERY accurate and have variables at the same time.. ------------- darf |
Posted By: briandarf
Date Posted: June-01-2020 at 10:44pm
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one more question.. how can you spin the shaft 180 and know for sure it didnt slide forward or back? ------------- darf |
Posted By: Gary S
Date Posted: June-01-2020 at 10:52pm
If I remember right one of the PCM books I have even mentions checking it every time it is launched as well. I believe their thinking was for large boats not trailer boats but that was not stated. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: KENO
Date Posted: June-01-2020 at 10:57pm
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Bdarf How can you really be sure of anything? Why didn't you update the thread in the link? You look for answers here, you really should finish your threads with an update  http://www.correctcraftfan.com/forum/forum_posts.asp?TID=48408" rel="nofollow - link |
Posted By: SNobsessed
Date Posted: June-01-2020 at 10:58pm
I used to put a .003 shim in the tightest spot, near a bolt hole. then tighten the bolt finger tight, just enough so the shim (aka spare feeler) wouldn't fall out. Then you can gage from there (.003-.006), rotating to see if it changes (it always did for me). ------------- “Beer is proof that God loves us and wants us to be happy.” Ben Franklin |
Posted By: 8122pbrainard
Date Posted: June-02-2020 at 7:58am
Brian, If the shaft slides forward or aft, then you slide it back and continue measuring. ------------- /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: GottaSki
Date Posted: June-02-2020 at 10:22am
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I think Brian's taking the 'measuring' too literal. Sub-0.001" angular alignment is possible, using any single feeler gauge in stack, by blunting the couplings together with the gauge inbetween and feeling for uniformity. After getting it close one then rotates each coupler individually to re-verify their squareness. if it goes wayout, stop and correct the flanges else chase it forever with bad results. then upon clamping the couplings, if it takes more effort to rotate the system, or has a difficult spot, something is still amiss and will translate to vibration or worse yet, failure. ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: Briandarflinger
Date Posted: June-02-2020 at 10:46am
| That's a great idea. Thanks!! |
Posted By: Briandarflinger
Date Posted: June-02-2020 at 10:47am
| Thanks gottaski. These are the answers I was looking for. You guys are awesome |
Posted By: 8122pbrainard
Date Posted: June-02-2020 at 11:15am
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Brian, Did you check your original shaft for straightness and if the coupling face was true to the bore? ------------- /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: 8122pbrainard
Date Posted: June-02-2020 at 11:16am
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One more, have you watched the alignment video? There's a link in the FAQ thread in the maintenance section. ------------- /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: Briandarflinger
Date Posted: June-02-2020 at 4:01pm
| Can't check the coupler the shaft is broken and still in it.. I guess I could check the shaft for straight if I had a glass coffee table. |
Posted By: 8122pbrainard
Date Posted: June-03-2020 at 9:23am
Brian, The alignment video has a short mention of using a dial indicator for checking the shaft. ------------- /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: MrMcD
Date Posted: June-03-2020 at 4:57pm
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To check for straightness you would set your shaft in 2 V blocks. Set up a dial indicator and you can slide the dial indicator to any spot on your shaft and while you rotate the shaft check for straightness. Not hard to do and no special surface needed. You can get a stand mount dial indicator for not too much money or borrow one. I keep one on hand, it comes in handy often. ------------- |
Posted By: SNobsessed
Date Posted: June-03-2020 at 11:27pm
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Take it to a pool hall & roll it on a table, they won't mind . . .JK! ------------- “Beer is proof that God loves us and wants us to be happy.” Ben Franklin |
Posted By: cpatton
Date Posted: June-04-2020 at 2:01am
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This happened to me a couple months ago. Take prop shaft out and find a flat surface (kitchen table, ping pong, etc.) and roll it across. If you see the shaft rolling with a warp it is bent and replace it. ------------- 1996 SS Nautique |
Posted By: 8122pbrainard
Date Posted: June-04-2020 at 7:27am
Colson, The max recommended TIR for a prop shaft is .003". If you can see that by rolling the shaft over a common table, I'd be surprised. Sorry but I don't feel your recommendation is sound. ------------- /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: Briandarflinger
Date Posted: June-11-2020 at 1:28pm
| New shaft installed and all seems ok!! I'm 90% sure the problem was both bad alignment AND seal was too tight.. my wax but had to be very loose in order for any water to cool it.. And by far the best way to align, is by bolting a shim in the tight side first,- that way you can observe both the + and - while rotating the coupler. .. I found out my engine was out of alignment from right to left, not just up and down. - when I rebuilt the stringers and floor, it three everything way off. Thanks for everyone's help... Now I have to figure out why it shifts so hard into reverse... |