|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? |
|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.
|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.
|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
|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)
|Well at least we agree on the important part |
GET A NEW SHAFT!
|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.|
|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?|
|my old drive shaft is a great pry bar now|