[C320-list] A High Pitched Whine Noise

[Melissa&Larry Leibman]

Dave,

I have had a similar noise on Easy Going for the last two seasons. The winter 
after we purchased her I applied antifouling to the prop using my usual Interlux 
application schedule and that season upon launching noticed the whining noise in 
a similar rpm range to yours. Coincidentally we had also changed the flax 
packing to GFO so I assumed it was related to that. However, after sticking my 
head down in the engine compartment I convinced myself the sound was coming  
from further aft than the stern tube and was likely from the propeller itself. 


The noise seems to be mostly an annoyance at this point and I generally just 
avoid that fairly narrow rpm range. A potential way to mitigate propeller 
singing is to chamfer the trailing edge. Although I did not do this on Easy 
Going, I did do a very modest flattening of the trailing edge this past 
off-season. I'm somewhat loathe to remove much material from the prop to avoid 
imbalance issues. After launch this season the noise was still there. It may be 
less, I'm not sure.

Here is a reference to a white paper with some information on the phenomenon if 
you are interested.

http://www.hydrocompinc.com/knowledge/whitepapers/HC138-SingingPropellers.pdf

Larry
Easy Going, #609