30 yanmar whistles

[CaptNHahn]

My 30 yanmar just started to whistle at 1800-1900 rpms. Not below that and not above that. Is there anything wrong?
Can I run my engine? Any ideas about what is going on? Had a diesel mechanic check it out but he could not find aynthing. It only happens when in gear not in neutral.

Thanks, Captain Nancy

 

[tlkenyon]

Mine did that.....it was a small air leak where the air filter cap did not seat correctly. At just the right RPM, it whistled. I am kinda deaf and it was a real challenge to find. Needed some youthful ears to assist.

 

[RProffer]

I would suggest it was an air leak. Could be a minor problem or it could be a major problem. If it is not the air filter cap, I recommend getting a mechanics stethoscope to locate the problem.

 

[Pete]

Are you sure it's coming from the engine? If it only happens in gear it may be a prop problem - slight bend, small nicks etc. can generate a whistling noise at specific revs that disappears at higher or lower revs.
Pete

 

[bbrh842]

My experience is same as Pete. I have a harmonic that appears around 1200 to 1400 rpm. I thought it was coming from the engine. A mechanic went for a ride with me and determined it was coming from the propeller.

 

[CaptNHahn]

Thanks everyone for replying regarding the whistle. Don't ask me how this happened, but I tightened the water pump belt ( not easy with the lower bolt) and the sound went away. 🙂

 

[RProffer]

Glad it was a simple fix. Learn something new everyday. Thanks for the update. Happy Thanksgiving.