How to Quiet Old Diesel

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fritz3000g
Posts: 178
Joined: Dec 8th, '20, 09:50
Location: 1982 CD 25D

How to Quiet Old Diesel

Post by fritz3000g »

I've got a Yamnar 1GM on my CD25D and it's very loud inside the cabin. I'm not really bothered by the noise, but I can't hear the radio or the radar alarm at all when the engine is on. Given that these are safety features, I'm concerned about that.

It's loud both at low and high RPMs, though a little easier to talk on the radio at low RPMs because it sounds like distinct thumps rather than a continuous sound.

Here's a pic of the engine mounts. Would replacing these help? A friend who replace his old engine mounts on his Beneteau made the engine much quieter.

Image

I've also read that worn main bearings can cause noise issues.

Anyone have success quieting your engine down?

I'm hoping to ask my mechanic when he's available, and am aware you can buy insulation to install between the engine compartment and cabin.
sgbernd
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Joined: Mar 3rd, '06, 11:53
Location: Valhalla
CD-28 #359
Ventura, CA

Re: How to Quiet Old Diesel

Post by sgbernd »

You can improve matters but not really succeed.

If you imagine noise is like water, it tries to escape every hole it can. That means to effectively quiet something, you need to put it in a nearly airtight container.

Unfortunately, to judge from my CD28, that is just about impossible. Behind the engine likes a nice big resonant cavity, below lies a bilge which carries the noise forward into the cabin, and to the sides are a couple of access panels which you need to keep clear for access to the rear of the engine via the lockers. Finally, there are a bunch of hoses, cables, wires, fuel lines, etc which all enter and exit the engine room from various points which are impossible to seal, not to mention the usual fuel filter, strainer, etc. mounted on the existing walls.

While I had the engine out, I tried to shield the front, top, and sides using that sound deadening material sold by Defender. It helped noticeably but you still can't hear the radio if the engine is at anything above a slow forward. Some guys have built plywood walls to block the aft of the engine which I think would help, but I am reluctant to restrict the already limited access, even if it is removable.

In summary, you can improve the situation to the point that you don't get a headache, but it will not be like a newer boat where the designers have designed the sound deadening in and you can talk on the radio under power.

Steve
fritz3000g
Posts: 178
Joined: Dec 8th, '20, 09:50
Location: 1982 CD 25D

Re: How to Quiet Old Diesel

Post by fritz3000g »

Thanks Steve! Looks like I should look at a remote radio and something to amplify the radar alarm.

Unfortunately it appears that I have a problem that might be related but more serious than just noise.

In this video, you can see the cam shaft is wobbling around, which according to my mechanic might be causing all sorts of issues including increasing the noise.

https://photos.app.goo.gl/Dhr36q9fUpb57Rfs7
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Frenchy
Posts: 620
Joined: Mar 14th, '15, 15:08
Location: CD 33 "Grace"

Re: How to Quiet Old Diesel

Post by Frenchy »

My guess is that the end of the shaft is distorted or bent somehow. The base doesn't seem to wobble. Those single
cylinder Yanmars do vibrate a bit. If you decide to change the mounts, remember that the front
and back are different.
Jean - 1983 CD 33 "Grace" moored in
Padanaram Harbor
Massachusetts
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gonesail
Posts: 233
Joined: Jun 22nd, '19, 16:39
Location: CD30 MKII FLORIDA

Re: How to Quiet Old Diesel

Post by gonesail »

those motor mounts don't look like yanmar mounts. maybe start by replacing them.
s2sailorlis
Posts: 387
Joined: Apr 9th, '14, 18:39
Location: 1984 Cape Dory 22

Re: How to Quiet Old Diesel

Post by s2sailorlis »

what was the rpm when taking the video? something sounds off. my last boat had a 3 y/o 1GM, i videotaped at diff rpm's...need to find it and see if the shaft was wobbly like that, IIRC it didn't.
______________
Rick
1984 CD22

Excuse auto-correct typos courtesy of iOS...or simply lazy typing
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Joe Myerson
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Location: s/v Creme Brulee, CD 25D, Hull #80, Squeteague Harbor, MA

Re: How to Quiet Old Diesel

Post by Joe Myerson »

FWIW, I have the same problem.
I've got a Yammer 1GM in my 25D. I've had the shaft replaced after an accident, and I had the motor mounts replaced, too. The engine runs well enough, but it's just too noisy for me to hear the VHF (I don't have radar). A number of years ago I replaced my radio with a very basic Standard Horizon model, and the speaker just isn't very loud. I relocated the radio closer to the companionway, but it still gets drowned out by the engine.

I mounted a small, inexpensive PolyPlanar speaker along the back of the cockpit, and it helped a great deal. Unfortunately, that speaker eventually succumbed to the weather. So, I am going to install a larger remote speaker, this time by Standard Horizon, in the cockpit. I'll probably modify the existing cutout for my speed log for the speaker, since It stopped working years ago. (In addition, the paddle wheel was only weed-free for about a week during the sailing season.)

Also, I keep a handheld in the cockpit--but the range just isn't sufficient.

Good luck!

--Joe
Former Commodore, CDSOA
Former Captain, Northeast Fleet
S/V Crème Brûlée, CD 25D, Hull # 80

"What a greate matter it is to saile a shyppe or goe to sea."
--Capt. John Smith, 1627
fritz3000g
Posts: 178
Joined: Dec 8th, '20, 09:50
Location: 1982 CD 25D

Re: How to Quiet Old Diesel

Post by fritz3000g »

Thanks Joe. That's what my mechanic recommended too. A remote speaker and remote mic.

s2sailorlis I didn't record the RPMs, but I suspect around 1000. It's with the mechanic and I'm hoping to hear why it's wobbly this week. If yours is wobbly (and especially if that's been ok) that would be very interesting to know.
Carl Thunberg
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Re: How to Quiet Old Diesel

Post by Carl Thunberg »

Sorry, I keep hearing about a radar alarm. What alarm are you talking about? My Garmin radar doesn't seem to have an alarm, unless I'm not using all of its features (which is entirely possible).
CDSOA Commodore - Member No. 725

"The more I expand the island of my knowledge, the more I expand the shoreline of my wonder"
Sir Isaac Newton
fritz3000g
Posts: 178
Joined: Dec 8th, '20, 09:50
Location: 1982 CD 25D

Re: How to Quiet Old Diesel

Post by fritz3000g »

Sorry, I keep hearing about a radar alarm. What alarm are you talking about? My Garmin radar doesn't seem to have an alarm, unless I'm not using all of its features (which is entirely possible).
Hi Carl, it's a proximity alarm. I can create an arc forward of my position (or a circle all the way around it) where any object that crosses it (boats, land, large birds - depending on sensitivity) set off an audible alarm. It would be really nice if I could hear it :)
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