Engine noises

[brak]

This year my engine started making a few new noises. I am fairly attuned to new sounds, but not too versed in engines aside from the basic service, so I wonder if anyone else has an idea.

Somewhere between 1100 and 2000 rpm the engine (or perhaps the transmission or the shaft, cant' be sure) makes a relatively high pitched "singing" noise, kind of a single tone of the same frequency and volume. It does not occur at lower rpm and it seems to disappear at higher rpm (though by then the usual engine sounds are loud enough that they may partially mask it, I am not sure).

I did not check if this noise is produced when the engine is not in gear at the same rpm (probably should have).

The engine is Yanmar 4JH2E.

[erps]

Did you recently have the propeller cleaned and worked on? We had a ringing prop after a haul out and a tuneup on the propeller. After the propeller grew some slime on it, the noise stopped. I made an inquiry about it on the C-34 website and found that it was pretty common. It was something to do with the sharp leading edge on the propeller creating some vibration.

Anyway, sounds like a noise between the prop and the transmission to me. You may be able to narrow it down using the stethoscope method.

[brak]

Curious. I had the propeller cleaned/primed/painted - it looks like new now. Never thought that'd be an issue

I'll try to localize it some more. It also did seem like the prop shaft is vibrating slightly - i.e. there is no vibration per se but it looks somewhat fuzzy near the transmission when spinning. I wonder if my engine lost alignment over the winter.

[erps]

Singing propellers:

http://www.hydrocompinc.com/knowledg...Propellers.pdf

[brak]

Yep, sounds very much like my case. I used a wire brush on a grinder to clean up the prop and while I didnt specifically sharpen it, it is certainly possible that it became somewhat sharper from cleaning.
Well, barnacles will grow on it soon enough.