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Thread: Vibration

  1. #1
    Member OKElkHunter's Avatar
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    Default Vibration

    I'm having a vibration when I put my engine in gear and fist start accelerating, also having a hard time getting on step. Boat is a 24' Bayliner with a 5.0 I/O Alpha 1. Running a 16" pitch prop but didn't have any issues until last weekend when we had a guest aboard and again this weekend with 2 guest. Had to move people around to get weight distributed just right so the boat would get up on step. I'm thinking a 14" pitch prop may fix the acceleration to step issue, but the vibration has me a little worried. Does anyone have any ideas what may be the cause of the vibration?
    “Don't expect to build up the weak by pulling down the strong." ~Calvin Coolidge~

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    You damaged the prop on the last trip without realizing it? Have you inspected the prop?

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    have you had boat for awhile and have you had others in the boat when you did not have step issues? Have you turned your prop when on the trailer to check is the shaft is bent?

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    U joints ?? turn your wheel hard over and put it in gear, listen for the growl.

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    Thanks for the responses. No damage to the prop; I check it each time in and out. Last two trips out we have had guest aboard and had step issues as well as vibration, 4 trips out before, we were alone and no issues or vibration. As soon as I felt the vibration, I suspected it could be a U joint, haven't done the hard turn test. Can I do that test out of the water with the engine flush attached, or do I have to do it in the water?
    “Don't expect to build up the weak by pulling down the strong." ~Calvin Coolidge~

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    Member DRIFTER_016's Avatar
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    First thing I thought of was the U-joints too.

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    Quote Originally Posted by OKElkHunter View Post
    Thanks for the responses. No damage to the prop; I check it each time in and out. Last two trips out we have had guest aboard and had step issues as well as vibration, 4 trips out before, we were alone and no issues or vibration. As soon as I felt the vibration, I suspected it could be a U joint, haven't done the hard turn test. Can I do that test out of the water with the engine flush attached, or do I have to do it in the water?
    in the water at idle.

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    A vibration and lack of power show up together.....Is this thing running on all cylinders? A missfire can and will cause both of these at once. How long has the 5.0 been running on that distributor cap, rotor, plugs, and wires? I'd be checking the basics first....like does it have compression, fuel, and spark. However, I was thinking ujoints too with the vibration.....LOL....

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    Mine was idling rough and would not get on step and it turned out to be the distributor had rotated as the hold down bolt was loose.

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    maybe the prop hub is starting to spin/slip ?? If your having problems when you load the boat heavier maybe the hub wants to spin ??

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    Great advice from all. Thanks everyone.
    I'll be making lots of checks over the next few days to isolate and fix the problem. This is the 2nd season on the distributer, wires and plugs. I should also check the timing too, it is idling a little low and gotten hard to start sometimes. Fuel economy has droppped off too.

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    Sure sounds like engine trouble to me. For a guest or two to make such a difference in a 24' I/O with no known prop damage, I'd have to guess you've got a serious loss of power. Easy to imagine a 4-banger turned 3-banger vibrating like crazy.

  13. #13
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    Not vibrating like crazy, just a mild vibration when you first put it in gear and start accelerating, smooths out as RPM increase. I am able to get up to MAX RPM once on step and I'm able to back down to 3800 and stay on step and maintain 22-23 knots with guest. No miss that I can tell. I'm starting to think its tune-up time and I need to check U-Joints. The 16 pitch prop is a little steep for a heavy load according to the prop guy. I have lots of checks to make, thats for sure, but the engine sounds good and idles smooth, just low.
    “Don't expect to build up the weak by pulling down the strong." ~Calvin Coolidge~

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    Quote Originally Posted by T.R. Bauer View Post
    A vibration and lack of power show up together.....Is this thing running on all cylinders? A missfire can and will cause both of these at once. How long has the 5.0 been running on that distributor cap, rotor, plugs, and wires? I'd be checking the basics first....like does it have compression, fuel, and spark. However, I was thinking ujoints too with the vibration.....LOL....
    Quote Originally Posted by BrownBear View Post
    Sure sounds like engine trouble to me. For a guest or two to make such a difference in a 24' I/O with no known prop damage, I'd have to guess you've got a serious loss of power. Easy to imagine a 4-banger turned 3-banger vibrating like crazy.
    Quote Originally Posted by OKElkHunter View Post
    Great advice from all. Thanks everyone.
    I'll be making lots of checks over the next few days to isolate and fix the problem. This is the 2nd season on the distributer, wires and plugs. I should also check the timing too, it is idling a little low and gotten hard to start sometimes. Fuel economy has droppped off too.

    BOAT: Break Out Another Thousand
    Yep, a V8 that loses 1 cylinder will turn into a very out of balance V7 and if there is crossfire igniton happening, all the worse. Is this a Vortec engine, or HEI and carb? About the engine sounding fine and idling smooth, ignition breakdown/misfire is often undetectable at idle (without a scope)and not make itself evident until the engine is under load. Having additional weight as you described on the past two trips could very well have been the tipping point to make the weakness noticeable to you.

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    Quote Originally Posted by .338WM View Post
    Yep, a V8 that loses 1 cylinder will turn into a very out of balance V7 and if there is crossfire igniton happening, all the worse. Is this a Vortec engine, or HEI and carb? About the engine sounding fine and idling smooth, ignition breakdown/misfire is often undetectable at idle (without a scope)and not make itself evident until the engine is under load. Having additional weight as you described on the past two trips could very well have been the tipping point to make the weakness noticeable to you.
    HEI with Carb
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    Picking up Tune up kit, plugs and wires tonight. Will check U joints also when I tune her up this weekend. Not taking her out again until the 4th, so I won't be able to put a load on her until then to see if my issues are gone. I should've tuned her up at the begining of season, when I de-winterized and changed all of the fluids. Lessons learned...
    How many hours do you usually get out of a tune-up?
    “Don't expect to build up the weak by pulling down the strong." ~Calvin Coolidge~

  17. #17

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    While you have the dizzy cap off, thoroughly check your coil and the connections as they frequently get corrosion that can cause all kinds of frustrating troubles....As far as how often to change caps, rotors, wires, and that junk, that depends on the quality of the parts, the number of hours, and the environment they are operating in. I don't think every year is necessary for most folks in Alaska as these parts last a good number of hours if high quality to begin with. But, if you put lots of hours on your boat and your engine is operating in a wet environment (which it probably is), the hours will be greatly reduced. Are you sure you have compression in all 8 holes? That's what I'd check first......If not, you're wasting your time putting ignition system parts into it. How old are your manifolds and risers? Just curious......

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    while in the distributor check the mechanical advance. The shaft should rotate about 20 degrees in either direction.

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    Manifolds and risers were replaced about 4 seasons ago. Got the cap and rotor off, pretty worn and I think there's about 4 seasons on them as well. Been a while since I worked on a V8, but now that I think about it, it is acting like it needs a tune up. I'm praying thats all that is the issue. Like I said, once up on step (plane), she runs just fine and will get up to WOT RPM and speed with no vibrations, but the fuel economy has dropped off. I'm also going to check all of my connections. I may also have a ground shorting someplace, my Tach/floscan has been acting up and blinking in and out. Gotta go thru some wiring as I do my other checks and maintenance.
    I have a mallory, breakerless, aftermarket distributor on the engine. Does anyone know where to get the marine grade distributer caps? I can't find one any place in Anchorage.
    “Don't expect to build up the weak by pulling down the strong." ~Calvin Coolidge~

  20. #20

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    I don't have an inboard boat anymore, and that is solely because of outdrive problems, manifold and riser problems, and how much everything seems to cost for them....It is like they are made of gold or something. Yours are probably fine at only 4 years.

    You know your boat and it probably just needs a basic tune. If you boat like I do, 4 seasons is around 400 hours of boating and that is quite a bit. If the caps are identical to OEM, and they probably are, I think West Marine can probably help you. I also think Burkeshore might have one too. Did you try NAPA? Sometimes they have boat stuff too.....

    I hope you get it fixed soon

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