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Transmissions vibration? |
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Gski 
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Joined: August-13-2021 Location: Wichita Status: Offline Points: 20 |
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 Topic: Transmissions vibration?Posted: August-15-2021 at 8:02pm |
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We were skiing the other day and after switching skiers next time we pulled up a skier we had a lot of vibration . The faster we went the more vibration. We didn’t hit anything and checked visually the prop,shaft and strut. Would a clutch or bad pressure plate cause this ? We could still pull skiers but didn’t want to do more harm. Oil in the tranny was good and smelled good. It’s a pcm 1:23 tranny. Looking for info or ideas
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8122pbrainard
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Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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Posted: August-15-2021 at 8:39pm |
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No "pressure plate" on a boat. Instead there's a damper plate bolted to the flywheel that connects the trans. From your description, I'd say it's going bad.
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Gski
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Posted: August-15-2021 at 8:51pm |
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Thanks I’ve been wondering what was up? How hard is it to change this out?
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8122pbrainard
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Posted: August-16-2021 at 6:40am |
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Glen,
It can be done with the engine in the boat. The aft end of the engine is raised enough to pull the bell housing and trans to get to the flywheel.
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KENO
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Posted: August-16-2021 at 6:51am |
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What model of boat are we talking about here?
I think that I'd pull the prop off and check the runout on the shaft right behind the strut before just jumping into a damper plate job. And if you have a spare prop, put that on and see what the results are. Also, check the coupling and shaft inside the boat to be sure everything is tight Does the engine run smoothly while this vibration is happening? Any extra noise or loss of power?
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Gski
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Posted: August-16-2021 at 9:03am |
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I’ve checked the motor and it’s running smoothly. I’ve also looked at the coupler it seems to be in good shape. If it is the damper plate would that create slippage and some added heat to the transmission?
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Gary S
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Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Posted: August-16-2021 at 9:19am |
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And now the rest of the story
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8122pbrainard
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Posted: August-16-2021 at 9:27am |
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Glen,
Kens advice is sound to check the prop and the prop shaft before anything. He mentioned runout aft of the strut. That's the spot that frequently gets bent and will cause the worst vibration. Max TIR in .003" so you will not be able to see it by eye. After the prop is removed, a dial indicator clamped to the strut works best. You will see nothing looking at the shaft coupling at the trans. Here's a picture of a damper plate so you may be able to understand what it does. As mentioned, it connects the engine and trans. The springs (inside the dimples) dampen vibration. There is no slipage.  BTW, you need to think more marine that automotive.  |
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KENO
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Posted: August-16-2021 at 9:52am |
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To finish the sentence above................unless the bolts are loose or you have some fretting going on and the shaft is working it's way out of the coupling. So I guess maybe you have some slippage and extra heat based on your last post? Does it vibrate in reverse gear or only forward gear? The answer to that will tell a lot as far as narrowing down your issue. Since you didn't answer the question about what the boat is, maybe it's not a CC, nobody around here really cares if it's a CC or not
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Gski
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Posted: August-16-2021 at 2:27pm |
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Vibration is more pronounced forward but that may be due to not using that much rpm in reverse. My question is would slippage seem more like a vibration especially as at 34 mph as aposed to 1200-1500 rpm in reverse. We’re pretty sure shaft and prop are good but I could put my spare on when I get it home. With the engine off I can turn the prop smoothly by hand, thinking it may not be bearings or such. By the way it’s a 91 ski brendella with pcm 351 and pcm 40a. It’s got 850 hours most all pulling skiers at 34 mph, I’ve had for 25 years.
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Jonny Quest
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Posted: August-16-2021 at 2:53pm |
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Based on the symptoms, it sounds like a damper plate that has imploded or a bent shaft (or both). 850+ hours and 25 years is about all one can ask of a damper plate. When they go, they can make a helluva rattle.
JQ
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Current
2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
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Gski
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Posted: August-16-2021 at 3:48pm |
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The boat is 30 years old but it had 118 hours when I got it. I’m not upset about it having problems , I just need to figure out what’s wrong and how to fix it. Winters coming and I hope to ski a bit more😎
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Gski
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Posted: August-16-2021 at 5:47pm |
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We’ll call me stupid ! I was fortunate enough for a marine mechanic to stop by and he found the problem quickly. The prop shaft is bent . I’d turned it a number of times and thought I had a good few. Guess I’m cross eyed. Thanks to all for your thought and ideas I’ll post after I get repairs done.
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KENO
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Posted: August-16-2021 at 6:21pm |
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I seem to remember somebody saying to check it We'll just call you smart for getting it checked  Now's the time to make your life easier and get a double taper shaft from ARE or General Propeller to throw out a couple of names. Cut the old one out inside the boat, and don't worry about getting the coupling off the shaft, you'll be using a new coupling with the new shaft. The double taper costs more and it's worth every penny in ease of installation and removal if you should need to remove it again in the future. Is this Brendella one of those boats with a Reverse Rotation engine spinning a LH propeller through the PCM 40A Call yourself lucky, you're not having to remove a transmission and all the work that goes along with it and you're hopefully getting a double taper shaft (that's the polite way of saying........spend the extra and get one) PS.........sometimes you pull the prop off and find a crack on the tapered part of the shaft where it's getting ready to break and send your prop to the bottom
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8122pbrainard
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Posted: August-16-2021 at 6:56pm |
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Glad you found the problem Glen.
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Gski
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Posted: August-16-2021 at 7:40pm |
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Yes it’s running a left hand prop. I’m getting the old shaft straightened and he’s also making a duplicate. They are already double taper shafts. The best part is my ski buddy does a lot of business with the guy making and straightening so I’m getting a real good deal. Also I’ll get a new strut bushing , I’ll install and test it out. This stuff I’ve been through before. It’s just hard to believe we didn’t feel when it got bent
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8122pbrainard
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Posted: August-16-2021 at 7:47pm |
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Maybe you weren't around when the shaft got bent? I've been through a couple of those "dad" moments. Since the shaft is bent, how's the prop and even more important the strut?
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KENO
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Posted: August-17-2021 at 6:25am |
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You didn't say where the shaft is bent, but if it's at the taper, I'd be looking real hard for any crack indications. Metal fatigue at the keyway, not hitting something may be the issue. I guess if it was mine and bent at the taper, I'd use it for a pry bar or a piece of wall art or something like that
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Gski
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Posted: August-17-2021 at 8:47am |
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I’ll find tomorrow. It’s going out to the same guy that straightened it out before. He does this and far more technical projects, but I hold the same concern. That’s why he is making another shaft.
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Gski
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Posted: September-06-2021 at 3:34pm |
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Up date , after removing the prop a crack was clearly visible in the drive shaft. I’m lucky I didn’t lose my prop. Long story short , I have a new drive shaft new strut bushings,strut is checked out and prop checked and true. I think the shaft cracked after being straightened before. I lapped the coupler and prop to the new shaft and realigned engine to the new shaft and boat is running smooth. Never felt a strike but maybe shaft just cracked over time. Thanks to all on ideas and commentary.
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8122pbrainard wrote: