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Old Jul 28, 2008, 06:04 AM
Registered User
Weare NH
Joined Nov 2007
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Uni joint

I just fired up my monaco and I noiticed that the motor vibrates at low speed.
The motor is lined up along the centerline of the boat with the propshaft.
I did noiticed that the motor is a little higher than the propshaft. The angle
is pretty close . i am useing a Graupner ujoint. Any ideal ?
Bob Big
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Old Jul 28, 2008, 06:29 AM
Is life for real?
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Almere The Netherlands
Joined Sep 2006
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Bob, your best (least friction, noise and vibes) alignment is a straight one, even then itīs advisable to use a double (two u-joints one cross/dogbones) or single (one u-joint/half a dogbone) u-joint to catch the vibes. Your motor is not suppose to vibrate, everything else might or is allowed (slightly!). Youīre sure you donīt have a loose motormount or loose motor on the motormount? Boo
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Old Jul 28, 2008, 06:35 AM
NeverAgainVolunteerYourse lf
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Australia, QLD, Regents Park
Joined Mar 2007
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Is it a double u-joint?, If its a single joint then vertical displacement is not good, a double can tolerate it,

are the ends of the uni concentric? that will cause the motor to wobble at low speed. Long shot are the motor bearings or shaft inboard bearings worn?

It also could be imbalance that resonates at low speed only?

A single uni joint can only have angular difference between the two shafts, a double can tolerate side to side or up/down differences as well as angular differences.

Regards
Nick
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Old Jul 28, 2008, 11:27 AM
Grumpa Tom
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United States, CA, Los Angeles
Joined Sep 2003
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Out of the box, the Equipage boats come with a stuffing tube that has some sort of plastic "bushings" that are neither concentric nor sized correctly. This means that brand new, it has play and the propshaft wobbles inside the stuffing tube. Run the motor for a few seconds and the plastic starts to distort exacerbating the problem.
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Old Jul 28, 2008, 03:22 PM
Naval gazing
United States, MA, Boston
Joined May 2008
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I've got some of those double U joints on my boat and the thing still makes noise.
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Old Jul 28, 2008, 04:44 PM
Registered User
Weare NH
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Quote:
Originally Posted by Kmot
Out of the box, the Equipage boats come with a stuffing tube that has some sort of plastic "bushings" that are neither concentric nor sized correctly. This means that brand new, it has play and the propshaft wobbles inside the stuffing tube. Run the motor for a few seconds and the plastic starts to distort exacerbating the problem.
I did have Boca Bearings int he frist Monaco no vibes .
I do not think i have the room for double uni I will look for loose screws .
Thanks guys
Bob Big
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Old Jul 29, 2008, 09:41 PM
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Rainhill UK
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Another alternitive is that it may be the wrong size Joint, there are so many sizes, a differance of 1/2 a mill will be enough. try backing the grub screw off and see if there is any play and that it is a tight fit.there needs to be no play with the grubscrew loose

Peter
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Old Jul 30, 2008, 06:07 AM
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Weare NH
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no losse screws the uin joint is tight on the motor and prop shafts. the motor bearings no play there. I think it may be do to the motor is a little higher than the propshaft.
Bob Big
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Old Jul 30, 2008, 10:40 AM
Naval gazing
United States, MA, Boston
Joined May 2008
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I remember 785boats told me once how he conquered the problem of Uni joint noise: heat shrink tubing over the joint itself. Not only does it work well but it looks cool. Well i dont know for myself that it works well but he tells me so. I'm thinking of doing that on mine. I'll let you know how that turns out.
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Old Jul 30, 2008, 05:02 PM
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Weare NH
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I went and looked again at low speed the motor tips back and forth
like it is on a hinge were the motor mount is bent.
Bob Big
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Old Jul 30, 2008, 05:06 PM
Naval gazing
United States, MA, Boston
Joined May 2008
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Quote:
Originally Posted by Bob Bighinatti
I went and looked again at low speed the motor tips back and forth
like it is on a hinge were the motor mount is bent.
Bob Big
Oh boy. Is it screwed on tightly? is the mount screwed down tightly? Is it autistic?
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Old Jul 30, 2008, 09:04 PM
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Rainhill UK
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Quote:
Originally Posted by Bob Bighinatti
no losse screws the uin joint is tight on the motor and prop shafts. the motor bearings no play there. I think it may be do to the motor is a little higher than the propshaft.
Bob Big
Thats not what I said , I said slacken the screws of , THEN see if the joint is a good fit on the shaft, if its the wrong size (loose fit) and you tighten the screws up it will vibrate like mad,,,you need the exact size for the shaft there are dozens of sizes and adapters, metric and imp

The coupling should be a reasonably good fit with the screws loose, no rocking movement, then tighten them to run.

HS93
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Old Jul 31, 2008, 06:17 AM
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Weare NH
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HS93 sorry Iforgot to say that the unijoint was tight with the screws loose on the shafts.
Bob Big
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Old Jul 31, 2008, 09:23 AM
can you land on that ?
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Quote:
Originally Posted by spacephrawg
I remember 785boats told me once how he conquered the problem of Uni joint noise: heat shrink tubing over the joint itself. Not only does it work well but it looks cool. Well i dont know for myself that it works well but he tells me so. I'm thinking of doing that on mine. I'll let you know how that turns out.
A variation on that is to eliminate the centre part altogether and use only a flexible tube like the Robbe coupling for smaller motors. I removed the centre from larger coupling and forced a silicon tube over the splines , no slippage and much quieter. The shaft and motor were lined-up pretty well before but to mind too noisy.
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Old Jul 31, 2008, 11:00 AM
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Kamloops BC Can.
Joined Jan 2008
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Havn't tried it yet, but the LHS sold me some tight fitting rubber tubing that he uses on his race boat for coupling the motor to the prop shaft. I was looking for the double u joint couplers. He says that he some times wraps a fine wire on both ends just to snug it up a little more, and it really cuts down vibration. Don't know for sure as I havn't tried it. Anybody else out there tried It?
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