Harmonics

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charlierusty123

Leigh Campbell
My 1973 Ericson 29 A4 emits a high pitched squeel or whine at the mid RPM in forward gear (usually somewhere between 800 and 1400 RPMs)

The previous owner says this is simple harmonics and there is nothing to be done but put up with it. Wonder if anyone else has this issue and if you agree with the diagnosis.

Thanks,
Leigh Campbell
 
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Rocinante33

Rocinante33

Contributing Partner
alternator?

I have observed this from an old, warn out alternator. The bearings were probably loose allowing the fan to rub against the case. I saw some small metal shavings accumulate beneath it. I could see a bit of forward/backward "woggle" of the alternator shaft and pulley. If you see that when you change the engine RPM's, you may have found your source of squeal. Then an alternator rebuild, or replacement is in order.
 
Gary Peterson

Gary Peterson

Marine Guy
Naw-Harmonics wouldn't be a squeal. Prop blade tips can squeal but usually at a very slow speed. I don't believe there is enough mass in the mass-elastic equavelant diagram to initiate harmonics or resonence in a Atomic 4 drive train. My opinion is either an alternator, alternator belt, or shaft seal.
My .1 Euro
 
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Bill Sanborn

Member III
I have the same problem on my 79 E29 w/ A4. It has done this for many years and I have never been able to find this cause. Always forward gear, low RPM but higher than fast idle. I also feel a light vibration in my feet. It seems to happen mostly when I first start out. It seems to be related more to prop rpm than engine rpm.

I have always changed RPM when possible to stop it.
 
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