vibration
Printed From: CorrectCraftFan.com
Category: General Correct Craft Discussion
Forum Name: General Discussion
Forum Discription: Anything Correct Craft
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=3073
Printed Date: May-10-2024 at 7:22am
Topic: vibration
Posted By: woodboy
Subject: vibration
Date Posted: February-21-2006 at 12:40pm
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I addition to my 79 Nautique, I also owd a 77 Century Arabian. The Arabian has a 351 mercruser with a V-drive trans. The boat has a vibration at low speed 5-15mph and not as noticeable at top end. Prop has dings and I havent aligned the motor. Any way to check shaft? 687hrs on boat. Any help would be great thanks to all> PS great site I've learned more here in two weeks than my 20+ years of boating! Also I lost 5-7 mph last season. The only thing I changed was A carb rebuild 2BBL rochester I know this post seems jumbled up but I cant seem to figure the loss of speed. Unless I hit something hard enough to bend prop or shaft. ------------- Lake Livin' Rocks |
Replies:
Posted By: 79nautique
Date Posted: February-21-2006 at 1:27pm
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the ding in the prop will hurt your speed a little, but I would say that the carb is why you lost the speed most likely it's a smaller carb or jetted differenty, that's assuming you exchanged it and didn't rebuild the one you had. If the shaft is orginal then you need to replace it. I believe they should be replaced after 500 hrs most people thing thay are good for ever and thats not true. Another thought would be that the cable could be adjusted differently than it was and you are not opening up the carb all of the way. I always did like the century inboards they seem to hold up well and and have a style that never goes out of date. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: jbear
Date Posted: February-21-2006 at 8:13pm
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Woodboy; Sorry for the hijack........
79; e-mail me when you got a chance. john ------------- "Loud pipes save lives" AdamT sez "I'm Canadian and a beaver lover myself"... |
Posted By: woodboy
Date Posted: February-26-2006 at 8:46pm
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79 the carb is orignial rebiult by an automechanic with 30+ years experience. I now just enough to get yself into trouble! I set the air fuel adj screws to 1.5 and 1.75 turns out with a dwell meter and still lack of mph are there internal adjustments that I'm overlooking? ------------- Lake Livin' Rocks |
Posted By: 79nautique
Date Posted: February-27-2006 at 7:09am
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Easy one since it's a rochester carb, On the idle air screws, screw them in slowly until the rpm drops slightly then back it out a 1/4 turn do this for both sides a couple of times until right on. You'll want to make sure you have the dwell and timing set correctly before you start messing with the carb. Replace the points with a elec. conversion kit or better yet a new electroninc dist. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: skyhawkflyer
Date Posted: February-27-2006 at 10:24am
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[QUOTE=79nautique] If the shaft is orginal then you need to replace it. I believe they should be replaced after 500 hrs most people thing thay are good for ever and thats not true.
Ya Right! Good advise. Change out a prop shaft that has nothing wrong with it. If your shaft is straight there is no need to change it out whether it's original or not. Don't listen to that crap. Bad advise. |
Posted By: 79nautique
Date Posted: February-27-2006 at 11:18am
That's how to quote and I guess you have never heard of the concept of metal fatigue or stress. They don't last for ever and the 500 hrs is most likely low. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
skyhawkflyer wrote:Posted By: skyhawkflyer
Date Posted: February-27-2006 at 1:21pm
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That's your opinion. Go try to sell that crap to someone else.
Ya, I understand stress. Especially when you have rock strikes. Maybe you should tear your engine down every 600 hours because it vibrates too. Hey, maybe the vibration causes stress... Maybe you should scrap the whole running gear then. Ya, right! 
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Posted By: 79nautique
Date Posted: February-27-2006 at 1:36pm
Glad to see your still the same ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: skyhawkflyer
Date Posted: February-27-2006 at 3:13pm
That was bad advise. Don't even try to play it off on me. Poor, poor advise. If the prop is dinged then for starters he should send the prop out and get it reworked or get a new one if he would like to upgrade. Curtis Prop can repair them for about $90.00 and check the cupping as well, which may take care of his problem. Chances are that if the shaft is bent it's going to get worse with vibration as speed/engine rpm increases. But first deal with the prop as it could have a blade that's been cupped from a prior impact. Just eyeing up the prop isn't good enough. While the prop is off you can set up a dial indicator mid-shaft to check for bends while rotating the shaft in nuetral, and also set it up at the tapered and as well when the prop is off. .001-.002 wobble is well within tolerance. Also checking the strut bearing for looseness. A loose support bearing will allow a prop thats been dinged to wobble as it rotates setting up a vibration. A prop that's been ever so slightly bent can take out a shaft support bearing in a few hours of skiing. No dial indicator? Rig up some sort of metal pointer to the shaft, such as tape some piano wire (or a sharpened pencil) with duct tape on your trailer cradle using a few 2x4's, rotate the shaft and you'll clearly see if it's bent enough to vibrate. Do it on the tapered end of the shaft as well, because the shaft isn't as thick there and can bend in the tapered area easier than the straight area. You can have a straight shaft and the tapered end bent, most likely caused by striking a rock at idle where the prop walked over the rock, causing the back end of the boat to lift up. |
Posted By: woodboy
Date Posted: March-02-2006 at 6:02pm
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Thanks for the advise guys. I think I will test the shaft first although .003 is difficult to see with primitive testing tools or a rigging like you describe skyhawkflyer. I did hit log last year hard enough to surface he log and nearly stop the boat at no wake speed! This was late in the season though ie loss of mph prior. 79N I have tried several settings with the carb starting at 1.25 out to 2.25 out I think over that is too rich. I did notice the fuel line is original and read a pin hole may cause loss of top end as well. Also the boat will not take off from "hammering" the throttle. It hiccups and sounds like a dead stroke no backfire at least I dont think it is unless the spark arrestor is a muffler as well ------------- Lake Livin' Rocks |
Posted By: 79nautique
Date Posted: March-03-2006 at 7:16am
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You may have to adjust the linkage for the accel pump, but check your fuel pressure, you may have a fuel pump going bad on you. Odds are the shaft is bent, maybe not thou, so get the prop fixed and see if you luck out and the vibration goes away. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: 64 Skier
Date Posted: March-03-2006 at 8:11am
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Woodboy, Did you change the carb or rebuild?
Does the accelerator pump linkage on the 2bbl adjust? If she hesitates during a hard throttle that's typically a sign of too little stroke on the pump. A light weight car (auto mechanic) will need less shot than a boat which typically pulls all the torque the engine will give up. Good Luck ------------- 64 Skier 66" HO VTX and 67" HO Triumph http://www.correctcraftfan.com/diaries/details.asp?ID=1071&sort=&pagenum=3&yrstart=1971&yrend=1975 - 71CC |
Posted By: woodboy
Date Posted: March-04-2006 at 8:48pm
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64 Skier: I rebuilt. I should say I had it rebuilt by an auto mechanic with 30+ years experience. He is an auto mechainc though. Any differnce with the marine two barrel? I've read the floats need adjusted on a 4BBl due to engine angle. ------------- Lake Livin' Rocks |