$5 part save me big time yesterday

A while back it was suggested by Pete to install a "shaft collar" and boy do I understand why now. Was cruising with the family yesterday and all of a sudden no power and motor revved fast. Popped the motor cover and looked down at the shaft and bam it was broke clean in half about an inch behind the coupler. We were in 100' of water and no trash in the lake anywhere just a pretty good chop on the water since I was in main lake. I would say the shaft collar at a minimum saved me a $400 prop and may have even saved sinking the boat if the prop had gotten into the bottom of the boat, pulled the strut off or damaged the rudder housing - who knows, but this was definately a life saver in my book. I am sure you guys will chime in with potential causes, but I am in the market for an ARE shaft now. Highly recommend that everyone out there invest $5.00 in a shaft collar if you don't already have one

I hear you Pete but, I just did the alignment a month ago and could turn the prop with two fingers that sucker was dead on - I thought about this all night and I think it was the lack of good heat fit on the coupler when I reinstalled a year ago - it took me two tries to get it to fit tight and my guess is that it lost a tight fit and was wearing the key until it created a misalignment issue - here is another pic of the key grooves and there is no evidence of the key anywhere.

Mark,
The black smut around the coupling/shaft is a classic indicator of fretting caused by bad alignment. If you got the alignment dialed in a month ago, it's quite possible the damage had already been done. How far out was the alignment when you did it?

It's interesting that so much of the keyway on the shaft protrudes from the aft side of the coupler (pic 2).

Also, on the same picture, just aft of the keyway slot on the shaft, are markings suggestive of the coupler fit.

But then on picture 3, we see the front end of the shaft flush with the front end of the coupler. Did the shaft break twice? Once toward the front of the coupler then slid out a ways then snapped again where we see it in picture 2?

I wonder if the keyway is rattling around inside the coupler between two pieces of broken driveshaft.

I just happened to see the link to this one today, so probably nobody will see this, but I had an experience with a broken shaft about 25 years ago on my old '81 Nautique. Unfortunately, mine broke about an inch in front of the strut, so the retaining collar didn't help. The prop slammed into the rudder, which immediately turned 90 degrees; this caused the boat to dive completely underwater at 36 mph. The skier had no idea what had happened as he skied past the "hole in the water where the boat used to be". The windshield broke from the force of going underwater, and the driver's seat was ripped completely off its mount. The water sealed the motor box to the floor, and the boat immediately surfaced, level with the water and with the hull completely full of water. I had apparently instinctively yanked back on the throttle, and the motor was still idling. Since I didn't know yet what had happened, I tried putting it in gear--of course, nothing happened! The motor continued to idle until it starved for air due to the intake tubes being full of water. After the bilge pump and manual bailing got the water out of the boat, I raised the engine cover and could see that when I put it in gear the transmission output shaft was turning, so that's when I realized either the shaft had broken or I had lost the prop. The torque of the prop being stopped by the rudder caused the strut to twist about 35 degrees, but the shaft was still in the strut. I replaced prop, shaft, coupler, and strut bushing, but was actually able to bend the strut back into alignment, and the rudder only had a small nick on it. Since water had gotten into the motor, I drained the oil as soon as I got home, then did a couple of back-to-back oil/filter changes with a little kerosene mixed in the oil. The motor ran great for another 7 years, when I rebuilt it after losing a valve spring. The break pattern on my shaft was a classic fatigue failure that had been building for a while; a small sliver about a quarter of an inch wide at one edge of the shaft was the last thing holding it together. I was always meticulous about alignment, and I think there was a flaw in the shaft that led to the fatigue failure.

Egon,
The safety collar goes on the shaft just forward of the packing gland. If the shaft breaks at the trans coupling, it stops the shaft from sliding aft. Since you sure don't want to have to pull the shaft to put a solid collar on, you can get split types. McMaster has them and in stainless too.

Breaking the shaft at the coupling is probably the most common spot. It breaking there is from misalignment.

I knew I would regret that question. Just found them.
Thanks

snipe wrote: I knew I would regret that question. Just found them. Thanks

I knew you would too

oldslalomskier wrote:    After my experience, I was thinking about inventing a method to retain the shaft in the event of a failure like mine, behind the retaining collar. That would require a secondary retainer below the hull, but in front of the strut--it would need to be tapered to avoid turbulence.

Already invented

had my shaft snap just forward of the prop hub, 35mph, 15 feet of water, (there is a slight chance we hit something) no obvious impact was felt, just lost power and came to a stop.

Mark,

I am not a good link guy, but goggle McMaster-Carr Supply Co. in Elmhurst, IL. On-Line Catalog . They have a large on-line Catalog that most plants / factories buy from. Correct Craft also put a lot of McMaster-Carr parts on these boats.

Donald

I found mine locally at Ace or TrueValue hardware - the big box guys no such luck. You might try your local store if your trying to get on the water this weekend

Thanks Guys. They had stainless, aluminum, one-piece, two-piece, everything you need.

On an unrelated matter - I knew my Purple and Teal Nautique would bring the NBA Hornets name and colors back to Charlotte!

74Wind wrote: The interior collar is a great idea. Questions: 1) With the collar installed, if the shaft were to break within the coupler, or anywhere forward of the packing gland, would the shaft (or remainder) go nuts within the boat and do damage? (although i assume any damage would be better than a shaft that has slipped thru the gland allowing water to flood in and a lost prop) 2) is there a recommended installation distance from the packing nut? 3)could the additional weight of the collar on the spinning shaft create, or aggravate, any previously un-noticed shaft wobble, or create any other issues? 4) i assume the split SS is the way to go, anyone know the original (I assume) shaft diameter on a 74 Southwind?

1) No, the shaft would still be retained by the coupling.

2) About 1/2" is enough to keep the prop out of the rudder.

3) No, the extremely small imbalance of the collar not being a perfect round will not be a problem. Think about the set screws running in the shaft coupling through all the years.

4) In 74 they didn't use safety collars.