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View Full Version : slight knocking sound coming from the shaft


jayderwin1
03-08-2005, 02:18 PM
has any one ever heard a slight knocking sound coming from some where around the shaft area when the boat is in gear at low RPMs?

Brn85ss
03-08-2005, 02:38 PM
Probably your dampner plate.If it goes away at higher rpm in gear thats probably it.Doing mine this spring should only take an hour or two.

jayderwin1
03-08-2005, 02:48 PM
can you explain what a damper plate is and does? mine will knock at the slowest RPM i can go in gear as soon i give it a little more gas the noise will go away.

Brn85ss
03-08-2005, 02:57 PM
Someone else might be able to explain this better than I, but here it goes.The dampner plate filters out the harmonic vibrations of your drive train when the springs start to wear or break that is the sound or rattle you here.Should be replaced right away so it does not put extra strain on the trans.Also if you have a slight miss in your engine it will sometimes make your dampner rattle.I'd make sure your engine has a full tune before your sure it's the plate.Chased this in my buddy's malibu,all it needed was a tune.Skidim has them for about 90.00.
Also it could be something else but this is pretty common problem,try to isolate the rattle.

jayderwin1
03-08-2005, 03:04 PM
is this plate located in the transmission? my engine also might have a slight miss but very slight if it does.

Professor
03-08-2005, 03:28 PM
Good Info. Our CC has been doing this for several years and runs great even though the motor has a zillion hours

Brn85ss
03-08-2005, 03:28 PM
The plate is in the bell housing,all it takes is a slight miss.

ski_king
03-08-2005, 03:29 PM
What is you idle speed?
Mine had a simular rattle, kicked up the idle about 100 rpm and it went away.

martini
03-08-2005, 03:34 PM
The plate is attached to the flywheel. It is between the transmission and the engine. The cast iron part(BELL HOUSING) that is between the engine and the transmission, is where you'll find the damper plate. Replacement requires lifting the rear of the engine a little to gain access to everything. An engine hoist should be used.

jayderwin1
03-08-2005, 04:35 PM
my idle speed is about 600 i goes up and down with how long the motor has been running.

ski_king
03-08-2005, 04:45 PM
When mine was making the noise it was below 600 and at a near stall condition. I was going to replace the dampner plate, but tried upping the idle to about 725 or so and replaced the dist cap, rotor, wires, plugs and it completly disappeared.

jayderwin1
03-08-2005, 05:18 PM
thanks for all the info i will try and tune up the motor first, changing out that Damper Plate sound like a bare