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WakeWorld Discussion Board » >> Boats, Accessories & Tow Vehicles Archive » Archive through January 14, 2005 » Runout on driveshaft « Previous Next »
By trash (trash) on Thursday, September 23, 2004 - 1:29 pm:    Edit Post Delete Post
I'm bringing in my driveshaft (already removed from the boat) in to get checked for trueness. Anyone know what the max runout is that's allowable?


By Sparky Jay (wake_upppp) on Thursday, September 23, 2004 - 4:10 pm:    Edit Post Delete Post
5 thou
By trash (trash) on Friday, September 24, 2004 - 7:23 am:    Edit Post Delete Post
Well, I brought it in to a machine shop last night. I found that the shaft isn't perfectly round, for whatever reason. The runout was consistent along the whole shaft except the small section after the cutlass bearing. They used a hydraulic press on it to try and straighten it. It is definately better at the end, but I think the middle might be slightly bowed now. (sigh)

I was hoping not to have to buy a drive shaft. I guess I'll wait until next year to put it back on and try it.


By Psyclone (cyclonecj) on Friday, September 24, 2004 - 11:13 pm:    Edit Post Delete Post
That sounds like you might have hit something with your prop at some point.

Have you guys ever replaced the cutlass bearing? My OM says to do it every 300 hours. I put 600 on mine so far, but I'm a slacker. No vibration problems and I'm in a pretty clean lake. Just wondering.

By Kevin R Baugh (krbaugh) on Saturday, September 25, 2004 - 8:20 am:    Edit Post Delete Post
What you have now is an almost straight shaft
That is weaker than before from being bent
Then bent back. I would always recommend a new shaft over one that is almost
Straight. IMHO If the shaft breaks you will be out at least a shaft and prop

By Dr. John (newtique) on Saturday, September 25, 2004 - 8:50 am:    Edit Post Delete Post
Kevin, I doubt the shaft was "weakened" by the straightening process (I'm a metallurgist), however, vibration is NEVER a good thing!
I'd bet that if you put a dial indicator on most inboards(after 100 hrs.), it would probably run-out 0.005".
My guess is that the shafts are centerless ground. It probably wouldn't matter a whole lot if the shaft were out of round a few thousandths, as long as it was straight.
Long story short......get a new shaft! Measure it on a surface plate and v-blocks before installation.

(Message edited by newtique on September 25, 2004)

By Kevin R Baugh (krbaugh) on Saturday, September 25, 2004 - 9:03 am:    Edit Post Delete Post
Well at least we agree on the important part

By Psyclone (cyclonecj) on Sunday, September 26, 2004 - 6:39 am:    Edit Post Delete Post
I read on here somewhere where a guy tore up a prop, put on a new 4 blade, and was out on the lake. The weakened shaft broke near the engine, and slipped out and sank. No prop, and a 1.125" hole in the boat. I'd replace the shaft.
By will clary (wakemaniac69) on Thursday, November 25, 2004 - 12:00 pm:    Edit Post Delete Post
I've replaced two shafts, the first measured 0.008" out, bent the prop on that one, I replaced the drive shaft only after haveing the prop redone. The second measured 0.024" out, again, bent the prop. I've discussed this at great lenghts with several machinists, and a certified Ski Nautique Technician. All agree, get a new shaft, straightend the old one and keep it for a spare. After straightening, they tend to go back to the bent postion after awhile. You can always use it for a backup in case you bend the current on. Anyone need a spare drive shaft for a 1980 Ski Nautique?
By salty87 (salty87) on Friday, November 26, 2004 - 7:21 am:    Edit Post Delete Post
my old drive shaft is a great pry bar now
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