[Question] Knocking/Clanking sound coming from flywheel/u joint area of jet
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Knocking/Clanking sound coming from flywheel/u joint area of jet

  1. #1
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    Default Knocking/Clanking sound coming from flywheel/u joint area of jet

    Hi,

    Is the first post always a question?  

    OK, I have a '74 Tahiti with a Berkeley 12JC-A pump and a BBF. There is some sort of sound that is similar to a knock although it just doesn't really sound like a piston knock to me... I've had a few engines in the past with genuine knocks. And it's stronger when I hold a screwdriver against the flywheel housing than it is anywhere on the engine. You can feel it on everything though, so it's a solid clank of metal for certain.

    We checked the timing (10 degrees at idle and it goes up to around 30 or more - the scale stops- at 3K rpm) that's good right? Added a bottle or race octane and new premium fuel as part of an anti knock attempt. Couldn't get race gas at the time. I didn't know about the whole disconnect a plug wire thing I read about recently and will check that next. But so far we don't think it's a knock... but of course, will continue to check that out.

    So far, none of the fuel stuff has changed the sound. Nor did messing around with the timing.

    The sound doesn't happen at idle and starts around 1K rpm. It sort of goes louder and softer as the rpm goes up. It's probably the loudest at around 2 to 2.5 K RPM. I also notice that after the boat is in the water running for about 15 minutes to 30 minutes it gets worse. Basically, we idle out to the fast water.... drive it around and try to hear where the sound is coming from and in that time it gets worse. But will still go away at idle.

    So far I was leaning towards something in the Flywheel/u joint connection to the jet but wanted to get some ideas from someone who maybe had a similar problem.... you know... a lot of the problems we have are common. And I don't know much about jets (yet) and don't know if the jet itself can make this kind of sound.

    Any help ideas are WAY appreciated!

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    Senior Member Widetrack's Avatar
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    Do you have room to disconnect the driveline? If so disconnect it and start the motor and see if it is still there! This will locate where the knock is coming from! Motor or pump!
    Check the oil filter to! Cut it open and look for metal!

    I had a Ford powered jet at one time that the riser was bumping the exhaust tip and it made a knocking noise at different RPM levels!
    Last edited by Widetrack; 07-18-2011 at 01:41 PM.


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  4. #3
    Senior Member H20MOFO's Avatar
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    Quote Originally Posted by wally-baby View Post
    Hi,

    Is the first post always a question?  

    OK, I have a '74 Tahiti with a Berkeley 12JC-A pump and a BBF. There is some sort of sound that is similar to a knock although it just doesn't really sound like a piston knock to me... I've had a few engines in the past with genuine knocks. And it's stronger when I hold a screwdriver against the flywheel housing than it is anywhere on the engine. You can feel it on everything though, so it's a solid clank of metal for certain.

    We checked the timing (10 degrees at idle and it goes up to around 30 or more - the scale stops- at 3K rpm) that's good right? Added a bottle or race octane and new premium fuel as part of an anti knock attempt. Couldn't get race gas at the time. I didn't know about the whole disconnect a plug wire thing I read about recently and will check that next. But so far we don't think it's a knock... but of course, will continue to check that out.

    So far, none of the fuel stuff has changed the sound. Nor did messing around with the timing.

    The sound doesn't happen at idle and starts around 1K rpm. It sort of goes louder and softer as the rpm goes up. It's probably the loudest at around 2 to 2.5 K RPM. I also notice that after the boat is in the water running for about 15 minutes to 30 minutes it gets worse. Basically, we idle out to the fast water.... drive it around and try to hear where the sound is coming from and in that time it gets worse. But will still go away at idle.

    So far I was leaning towards something in the Flywheel/u joint connection to the jet but wanted to get some ideas from someone who maybe had a similar problem.... you know... a lot of the problems we have are common. And I don't know much about jets (yet) and don't know if the jet itself can make this kind of sound.

    Any help ideas are WAY appreciated!
    I had a waaaay nasty noise 1st of the year...pretty much intermittent..fwiw...mine turned out to be my new starter was a hair to close(front to back...not up and down) to the flex plate. Good luck.
    Another Hot Boat refugee

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    Senior Member bp298's Avatar
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    can you see the driveshaft/h-bar?? or does this thing have a 3 point mount bellhousing that covers the shaft/bar?????

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    Quote Originally Posted by bp298 View Post
    can you see the driveshaft/h-bar?? or does this thing have a 3 point mount bellhousing that covers the shaft/bar?????

    There is a bell housing that covers the most of it up. There's a plastic plug about 3 or 4" wide that you can take off where you can see inside the housing. I can see something that looks like a U-Joint in there. Is that the H bar? It looks like the connection I saw in the YouTube video from cp performance on how to install a Jet pump in a boat. And, there is a cover over another spot on the housing where you can see the teeth in the flywheel. I'm thinking this was another spot to mount a starter maybe.

    My next plan was to take off the housing and try to see what's going on. Hoping to be able to disconnect the engine from the pump without having to take the whole thing off.

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    I had a noise just like what you're describing...turns out the flexplate was loose. Seems to me if you can't for sure locate the noise, you will definitely have to dis-connect the driveline...ergo, pull the engine

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    Sounds like a 3 point mount. If you have an engine hoist, pull the bell housing and remove the driveline. Reinstall the bell housing and see if the noise goes away. You can check the torque on the flywheel/ flexplate at this time as well. If you don't know the condition of the universal joints its wise to rebuild the driveline as well.

    Without the engine hoist, you might be able to wedge some wood blocks under the oil pan so you can remove the bell housing.
    "He is a lover, not a fighter. But he's also a fighter, so dont get any ideas."

  10. #8
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    May not have read enough here but sounds like an engine related noise (more than a jet or DL ) hope I'm wrong Tom

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    Quote Originally Posted by wally-baby View Post
    There is a bell housing that covers the most of it up. There's a plastic plug about 3 or 4" wide that you can take off where you can see inside the housing. I can see something that looks like a U-Joint in there. Is that the H bar? It looks like the connection I saw in the YouTube video from cp performance on how to install a Jet pump in a boat. And, there is a cover over another spot on the housing where you can see the teeth in the flywheel. I'm thinking this was another spot to mount a starter maybe.

    My next plan was to take off the housing and try to see what's going on. Hoping to be able to disconnect the engine from the pump without having to take the whole thing off.
    If the bell housing is sitting on the pump, you have a three point mount. You will have to use an engine hoist to hold the engine up or rig something to hold the engine while you take off the bell housing.

  12. #10
    Senior Member OkieDave's Avatar
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    Default flywheel bolts

    loose flywheel bolts.

  13. #11
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    I'm guessing the grease worms got to your u joints
    #55

  14. #12
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    Quote Originally Posted by wally-baby View Post
    There is a bell housing that covers the most of it up. There's a plastic plug about 3 or 4" wide that you can take off where you can see inside the housing. I can see something that looks like a U-Joint in there. Is that the H bar? It looks like the connection I saw in the YouTube video from cp performance on how to install a Jet pump in a boat. And, there is a cover over another spot on the housing where you can see the teeth in the flywheel. I'm thinking this was another spot to mount a starter maybe.

    My next plan was to take off the housing and try to see what's going on. Hoping to be able to disconnect the engine from the pump without having to take the whole thing off.
    if the bellhousing extends back to, and rests on the end of the pump, it's a 3 point bellhousing. you cannot get it off without pulling the engine forward (pulling the splined coupler away from the pump) and lifting the engine. the bellhousing should have a clamp around the flange on the front of the pump, which is secured by two bolts inserted from the bottom.
    if it's an engine knock, your going to need to remove the engine from the boat to fix it. if it's flywheel/driveshaft related, your going to need to remove the engine from the boat to fix it. trying to remove that bellhousing with the engine still in place is futile.
    it's not that big a deal to remove the engine. just takes a little time.

    pictures would be helpful...
    Last edited by bp298; 07-19-2011 at 10:52 AM.

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    Based on the limited info at hand, I would check the PTO/U-joints, Flywheel bolts or if your running a flex plate, check it for cracks..

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    Quote Originally Posted by ezobens View Post
    Based on the limited info at hand, I would check the PTO/U-joints, Flywheel bolts or if your running a flex plate, check it for cracks..
    Yup - this is what I'm gonna do next. I just brought my engine hoist over here and gotta get the boat off the hydrohoist and on the trailer ect... I'm gonna post what happens next for sure.

    Thanks all!


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