Viberation - was driving at speed.

Brett - I have gotten similar sudden vibrations & I think it was fishing line or seaweed, as it went away when I stopped & put it in reverse.

1st - check to make sure your prop is not loose & the lock nut & cotter pin is there.

Then check your shaft coupler & screws to make sure those are tight.

When something changes suddenly, it is usually a simple cause.

PS - Last year we hit a log & it bowed the shaft but did not harm the prop. Hard to believe but true.

you would definetely feel if you hit a log or something strong enough to suddenly make the boat vibrate...

you may be experiencing shaft whip also, slight bend but aggravated by RPM's

Thought I would continue this thread instead of starting another.

I'm having similar issues as this post. I have done my usual google search "correctcraftfan.com sudden vibration", which usually gives great results, but only came up with a couple threads. Another one here but that is almost the opposite of what I experienced. And and this one here is almost to a T what happened to us yesterday.

I have come here today just to verify that i will be attacking this in the proper way, aka testing and not throwing parts at it!

so our story, after about an hour on the river, we were traveling at 23 mph in a straight line and instant vibrations. immediately reduced throttle to neutral with no vibration. put it in reverse (detent, no additional throttle), without vibration. Everyone on the boat all said the same thing, "sure didn't feel like we hit anything." The vibration is only evident over 1.2k rpm, but never pushed it over 2.5k as i was afraid it would cause more damage. Idled back to marina. prop "looks" fine. drive shaft "looks" fine. spun the prop/shaft and didn't "feel" any binding or notice any bends in the shaft. Engine revs up in neutral without vibration. Popped the access panel and you can definitely "see" the vibrations in the rubber coupler just aft of the stuffing box.

1. So my first step i will take is to check prop nut for tightness and/or change out the prop to make sure the prop itself isn't unbalanced (the testing prop when last used caused no vibrations).

2. Based on the other thread, i can check for water in the fuel. Not sure how to do this, so I'll keep looking through other posts.

3. Check shaft packing, shaft coupler screws.

4. Check cutless bearing (not sure how to do this)

5. Check shaft alignment? Any recommendations for the best tool and where to get it? do places "rent" them? I've prolly watched Pete's video 20 times when i first joined this site, so at least I'm somewhat familiar with that resource. If this ends up being the case, is the only solution a new drive shaft or can a machine shop straighten it?

And just for piece of mind, are the symptoms generally shaft/prop issues or could this be a transmission issue? And if a prop/shaft issue, can the boat still be used at least at 20 mph or less or would the continued vibrations lead to further problems/damage? Not that I won't fix whatever is wrong, but with the holiday this weekend, we want to be able to cruise the river with the family.

Thanks in advance for any feedback.

Joe,
Since you mentioned you didn't notice any binding of the shaft, I'd say the alignment is good but it's a good idea to check it anyway. After you check to make sure the prop was seated properly to the shaft, the next two suggestions are to check the shaft for straightness and have the prop checked. Both can and will go at anytime seemingly for no reason and without hitting anything. Shafts are known to completely break off and typically just aft of the strut. Check the shaft at the tail end with a dial indicator. Anything over .003 isn't good.

Bad alignment typically does not cause vibration. It actually has the opposite effect sine it's putting a bind on the shaft snubbing vibration.

SNobsessed wrote: Well, best to use logic to figure out what could change going along at steady state. Is your Tranny fluid OK?     Any engine mounts work loose? (this happened to me, obviously I didn't lock them tight enough). Definitely check alignment & cutlass bearing. Maybe even check packing gland, I have heard of these rubbing the shaft on the inside.

yes, tranny fluid was still ok. I actually check that before we leave the marina each outing (along with the oil). But did check it right after "the event" just to see if it had been leaking or anything and it was still at the same level. Blige shows no sign of leakage either.

After reading Pete's post, i misused the term alignment in my head. I realize now there is alignment with the tranny, but I was actually thinking shaft straightness. What is a recommended dial indicator and/or can i rent one from an auto store? if it is off the specs, can a shop straighten it or is it a new part purchase?

Tim, yeah, i would agree, i haven't ruled out the prop and prolly the easiest to test. However, the props have recently been repaired and were in waaaaay worse shape without vibration. I also didn't rule out that we hit something, but there wasn't any sort of thud, jerk, bump. The speed of the boat never changed, just the sudden vibration. Enough the back floor was vibrating.

We were with another couple and it was getting late, so I didn't spend a lot of time investigating. Just a quick look and spin of the prop and looked over the hull for damage. I plan on doing things the best i can in the evening, but any water tests will have to wait until thursday.

Thanks for the quick replies.

Thanks Pete. Glad to know cheap is ok here :)

I'll go through as many steps as i can tonight if time allows. The SeaDek for the bow arrived today, so that might get done as well.

Joe,
Your videos are marked private but, your pictures are enough for me to comment. I should have been clearer on where to read any runout with the dial indicator. I mentioned "tail" end but I should have said at the very end of the taper just before the threads. The spot were you are taking the reading is where the shaft typically bends so if the shaft is bent, you wont see any or not much runout. Each "tick" is 1 thousand .001" Since you are getting 2 ticks just aft of the strut, then I suspect the shaft is bent. Reposition the dial indicator and report back.

vids fixed.

good catch on the burr. glad i took the video. you can see so much more than when initially doing it. I can move the dial, but the keyway slot is only about a 1/4" from where the dial is now and thinking about it, i have a picture in my head that the slot extends into the first part of the treads. but i could be wrong so ill check again tonight.

Spray some soapy water on the cutlass it will make turning the shaft a lot easier.

Joe,
I would concur that the shaft is bent. Did you sent the prop out to a prop shop? If so, report back what they find. It may not be the end of the season yet since depending on what they find, it may be worth taking a chance.

8122pbrainard wrote: Yes, you can straighten a shaft but, with the advent of the ARE shaft system, I personally don't feel it's worth straightening.

Well, i have a few things going against me. I had both the 3 and 4 blade props repaired mid-season last year. The prop guy i used is up north in GB and i have no plans to head up there (so i'd have to ship it). I've been using the 4 blade, so at least the 3 should still be good to go. I'll still test that out on Thursday.

As far as a machine shop, the one in town has already been working on a new set of ex. manifolds for the past 2 months. Apparently he is really busy, soooo I'm guessing this wouldn't be high on his priority list. All other shops would be drive time, which i don't have that much of during the week.

Plus, the Mrs has already put the kibosh on extraneous boat expenditures, it was hard enough to work fuel into the budget (at least I won fuel). I can't comprehend how she won't put boating above groceries????

I'll probably take my chances over the weekend as at least in idle gear there wasn't vibrations. Just need to make it to the anchor spot and back. It'll probably be a few weeks before i get answers to the rest of it. I guess now is a good time to install the SeaDek in the bow. Stay tuned for that thread

Eek, I guess I would have saved my money on the SeaDek if the boating budget was THAT tight.

I'm sure I have at least one used 54" shaft I could sell. Bring your nifty dial indicator and come measure it.

you might want to bring lube

or not

Well, got some good news to night. Took the boat out for 45 min. Started slow. No wake speed, then we just kept bumping it up 100 rpm at a time. Noticed a little vibration in the exhaust hose, no vib at the rubber coupler. Got it up to 2500 and still no vibration like before. Then got it up to 4000 without issue. Took it back to 3000 and ran for a good 30 min like that. Seemed solid the whole time. So im gonna say our issue was the prop. Still gonna try and get a shaft for a spare. 4-blade is already on its way to the shop to be tested. Thanks again for everyones help.

3-blade test