R21 engine noise suppression

[donnevin]

Is it possible to obtain or build an engine cover which will allow quieter operation. Love the boat but need to knock it down a few decibels. Any suggestions appreciated.

 

[bob daily]

Subject has been discussed on this forum in the past, you might want to do a surch on the subject,
I usually just turn my hearing aids off and the noise doesn't bother me, it also masks the chatter comming from the crew which I usually ignore anyway. Bob

 

[lproulx]

This is a tough one. Part of my father's career dealt with industrial noise hazards and suppression, so I learned a little.

The basic problem is you are always too close to the engine. It is blessedly quiet up in the bow, but you can't spend all your time up there. I purchased some sound deadening material that consists of a sheet of dense, heavy material sandwiched between two layers of foam, total about 2 in thick. I lined the entire motor box with it. It rubs on the Volvo coolant expansion tank a bit when you open and close it. Don't know how it would work on a yanmar. I would say subjectively it made a 20% improvement. A diesel engine just runs inherently rough and creates a lot of low frequency vibration that gets transmitted to the hull. There's no way to filter it out or block it out. There seems to be a sweet spot about 1800 rpm that gives decent speed and less obnoxious noise.

I sometimes wonder if a 4 cylinder engine would have been better. Our yacht club launches have Westerbeke diesels that seem to purr like kittens by comparison.

Sorry I could not offer more encouragement.

Larry

 

[donnevin]

This is a tough one. Part of my father's career dealt with industrial noise hazards and suppression, so I learned a little.

The basic problem is you are always too close to the engine. It is blessedly quiet up in the bow, but you can't spend all your time up there. I purchased some sound deadening material that consists of a sheet of dense, heavy material sandwiched between two layers of foam, total about 2 in thick. I lined the entire motor box with it. It rubs on the Volvo coolant expansion tank a bit when you open and close it. Don't know how it would work on a yanmar. I would say subjectively it made a 20% improvement. A diesel engine just runs inherently rough and creates a lot of low frequency vibration that gets transmitted to the hull. There's no way to filter it out or block it out. There seems to be a sweet spot about 1800 rpm that gives decent speed and less obnoxious noise.

I sometimes wonder if a 4 cylinder engine would have been better. Our yacht club launches have Westerbeke diesels that seem to purr like kittens by comparison.

Sorry I could not offer more encouragement.

Larry

Thanks very much!

 

[donnevin]

Subject has been discussed on this forum in the past, you might want to do a surch on the subject,
I usually just turn my hearing aids off and the noise doesn't bother me, it also masks the chatter comming from the crew which I usually ignore anyway. Bob

Perfect solution. Sorry for late reply