Yanmar 4JH3E High Pitch Whistle

Moon Eye is a 2004 IP370 #21. Her Yanmar 4JH3E with 1480 hrs has developed a high pitch whistling sound at 2300 to 2700 rpms. She is quiet and smooth running above and below that range. It only happens in forward, not neutral. We are southbound on the ICW from Maine to Florida. Adjusted stuffing box. That did not solve it. Motor mounts were replaced and engine aligned after that a year ago. There was no whistle before that and none until we started putting her to hard use on this trip. Cutlass bearing was ok at recommissioning in June. Comments?

Do you have a vented loop coming off your mixing elbow? If so, there is a small vent at the top of the "U" pipe. That vent can "whistle" when the water flow is fast enough (ie: higher rpms) if its not working properly or cracked.

Rick
We are original owners of 370-24 also with the 4JH3. First, Google "singing prop" and read some other owners experience and the science behind the problem. Then my story. It may or may not of course apply to your boat.

For the first 4-5 years of ownership every Spring after our haulout and with a completely clean prop we had a high pitched "singing" between 1300-2200 rpm. Within a few weeks it would go away and only return in late summer after the diver had cleaned the prop and wiped the bottom. Several mechanics took short rides and heard the sound - checked alignment, motor mounts, but no change.

I then by chance the next Spring mentioned this to the owner of the marina where I haulout and he said I think you have a "singing prop". We pulled the prop and I took it to the Norfolk prop shop and the owner there said I can cure this by a slight camber on the trailing edge and actually gave me a copy of one of the scientific papers you will find online. Indeed he did - problem gone.

The other comment about the raw water vented loop is also interesting. It reminded me that Island Packet issued a factory service bulletin for our 370s to fix a problem in that the hose from the raw water vented loop to the bilge as installed at the factory did not continuously run downhill, allowing water to block air flow. They sent me a new hose and a few other parts and the new way to route the hose that I installed myself. If you are not the original owner you might check to see if that was done on your boat.

Enjoy your ICW trip. Done it twice and some wonderful places to stop and enjoy along the way.

Harry Burns
IP 370-24 Two for the Roads

We completed our trip from Maine to Florida. The high pitch whistle continued. It didn't get any worse but it didn't go away either. I talked to the IP factory, Michigan Propeller (the prop manufacturer), and two highly recommended prop shops. All agreed the "singing prop" you described could be the cause. I had the prop pulled, refurbished and balanced. They added a camber to the leading edge of each blade to stop the harmonic whistling. We'll get back to the boat in February . Hopefully this fixed it. I'll keep you posted on the results.

This is a follow up to my posts 9 months ago regarding a Whistling prop. The prop shop added a camber to the leading edge of the prop. This appears to have solved the problem. Our sea trial was successful, no whistling anywhere
through the rpm range. A family illness caused the 9 month delay and prevented us from getting back to the boat to run the sea trial,