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FAQ: Engine Noise and Vibration

 

 

Can I keep the Engine Noise and Vibration down?

 

Original Message:
Subj: Engine Noise and Vibration
When I bought my C34 I was thrilled with how much smoother and quieter 4-cylinder M35 diesel was compared with the 2-cylinder M18 that my C27 had been equipped with. On long passages, more often than not I end up motoring a lot and motoring in a sailboat is not especially fun. I was beginning to consider switching to a powerboat. Since I end up powering so often anyway, I figured I might as well get there fast. Recently, I had an opportunity to sail aboard a new Hunter Passage 420 with a 62hp Yanmar diesel. I don't know if its characteristic of Hunter's engine installations, Yanmars in general or something unique about the 420 and/or the 62hp Yanmar but it was incredibly smooth and quiet. I actually tried to start the engine after it was already running because I couldn't hear or feel it. I decided that I'd enjoy weekend passages under power much more in a sailboat that ran that smooth and then, of course, I could still sail when conditions permitted.
Now, I must say that I was surprisingly impressed with many aspects of the Hunter but I can't easily envision myself owning one, primarily for aesthetic reasons. My question is how smooth and quiet are the engines installed on the larger Catalinaís? My local dealer just sent me some specs on the C380. They scratched out the reference to the 4-cylinder 42hp engine and wrote in a 3-cylinder 40 hp. Seems like they're going in the wrong direction.
Also, does it pay to try to improve the noise and vibration isolation of my present engine? If so, which modifications provide the greatest improvement?
Engine mounts? Drivesaver? Additional soundproofing? Evolution Marine Shaft System? Others?
Bob Greenhaus, "Summerhaus", 1994 C34MkI, #1290 TR/WK, rgreenhaus@omnisky.net
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Subj: RE: [cat] Engine Noise and Vibration
You have soundproofing now? My 92 C-28 was delivered with an uninsulated engine cover. You couldn't have a conversation in the cabin without shouting when the engine was running. I insulated the 3-sided cover with an industrial grade soundproofing material, and you can now have a conversation without shouting. My next step is to insulate the head and rear cabin bulkheads. Unfortunately I can't use the same material because there is inadequate clearance and the insulation is 1-5/8" thick. I've seen similar products sold at retail (foil face, with a decoupling layer). They are expensive but they do an excellent job.
John Cairns, C-28, #194, "TALISMAN", jcairns2@visteon.com

Subj: Re: [cat] Engine Noise and Vibration
Yes. It appears that the C34 is well soundproofed except for the access panels from the head and the aft cabin. There doesn't seem to be sufficient clearance to soundproof these surfaces. The impact of vibration seems to be greater than that of direct engine noise. The vibration generates sympathetic vibrations in lockers, drawers, the stove, hasps, fire extinguisher brackets, etc. I've wrapped the fire extinguisher bracket and sail locker hasps with self-bonding sail tape and installed pads on the companionway ladder feet and on the head and aft cabin door frames to prevent vibration. I don't have what I would consider to be UNUSUAL noise or vibration. No shaft or prop problems. Shaft is aligned well. Compared to many boats mine is smooth and quiet. Unfortunately, I've seen just how smooth and quiet a sailboat can be under power and I liked it.
Bob Greenhaus, "Summerhaus", 1994 C34MkI, #1290 TR/WK, rgreenhaus@omnisky.net
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Subj: Re: [cat] Engine Noise and Vibration
Bob: you have described the EXACT thoughts I have regarding the '91 C34 / M35A. The engine compartment is about as insulated as you can get it given the room and clearances. Most of my complaints would go away if could just stop the harmonic vibrations the engine sets up at several rpm ranges. As you describe, everything that is not bolted/glued down from the engine compartment / hatch back vibrates. These are not shaft alignment vibrations as they occur in the same ranges whether in gear or sitting in the slip in neutral and the shaft is aligned per specs.
Maybe it is the Yanmars?, a friends Cal28 with a 2 cylinder Yanmar is smoother/quieter motoring than the C34 with the M35A.
If anyone can come up with a reasonable solution to this problem, they will probably make a lot of C34 owners happy.
Jack, C34 # 1169, Port A, TX, asailorir@earthlink.net

Subj: Re: [cat] Engine Noise and Vibration
Bob: I found a Yanmar page, which speak volumes without saying a word. The only say "Low Vibration" on the 3 cylinder units; vibration goes without mention on the 2 cylinder and 4 cylinder units. I think 3 is an odd number to balance.
Phil Agur, C270 LE #184, "WING TIP", pjagur@directcon.net

Subj: Re: [cat] Engine Noise and Vibration
I think that the vibration has a lot to do with the engine mounts. With one exception, I think that just about all of the Catalinaís I've seen (and many others) are using some sort of "hard" mount directly tied to the stringers in the hull sections. The one exception that I sailed was a 470 in which the engines have been isolated from the hull. Sort of like a car which uses a rubber and steel sandwich type system. My 400 is not all that bad, but the 470 was a totally different story - a lot better and probably comparable to that Hunter. I wonder if they did the same thing to the 400 Mark II when they dropped the Yanmar in. Cars have been using this type of system for 50 or 60 years - it's about time that they do something similar for us. I think the powerboats are a lot better at this kind of stuff too. Most sailboat manufacturers seem to treat auxiliary power as an afterthought.
As far as noise goes, the insulation on the forward cover is decent, but there is absolutely nothing on the back cover. I bought some foil / padding a few years ago, but never installed it. One of these days.
Ron Marcuse, C400 #74, "Good Vibrations" (and too many of them), CaptRon400@aol.com

Subj: Re: [cat] Engine Noise and Vibration
Actually - 2, 3 , 4 and 5 cylinders all present some of problems with harmonics. A straight 6 is the easiest to balance - V6's and V8's require some work too. I'm referring to internal counterweights and balance shafts along with firing order and a thousand other things. Assuming that the engine manufacturer has done his homework (some probably haven't), then its up to the builder to isolate it in the car, boat or ?? Bolting it directly to the fiberglass grid (maybe using a little piece of rubber under the mount) is not sufficient.
Ron Marcuse, C400 #74, "Good Vibrations", CaptRon400@aol.com

Subj: Re: [cat] Engine Noise and Vibration
I almost forgot about the vibration. While I was looking at some info on feathering props, I bumped into this. http://pyiinc.com
John Cairns, racko@home.com

Subj: Re: [cat] Engine Noise and Vibration
John: Thanks for the link. I have a MaxProp and I'm familiar with PYI and their vibration products. Just don't have any idea how well they actually work.
Bob, C34 #1290, rgreenhaus@omnisky.net

Subj: Re: [cat] Engine Noise and Vibration
A friend of mine just took delivery of a new 470. He told me it was incredibly smooth and quiet but I haven't had an opportunity to hear it for myself yet. He did demonstrate the generator to me -- itís very quiet and smooth. Only the sound of the splashing exhaust water signals that itís running.
Bob, C34 #1290, rgreenhaus@omnisky.net

Subj: Re: [cat] Engine Noise and Vibration
I have a 380 with the 42 HP 4 cyl Westerbeke. The 4 cyl is much better than the 2 cyl I had on my 31 foot Benetau. I put extra noise reduction in the engine compartment and am planning to install a flex shaft coupling. There are two areas that generate the noise, one is direct radiated noise and the other is the vibration coupled to the hull through the mounts, shaft etc. My boat is very comfortable when under power. Still, a little noise below but in the cockpit everything is quiet. I expect when I install the flex coupling my 380 will be almost as quiet as the Hunter you were on.
Gary, Gcooper288@cs.com

Subj: Re: [cat] Engine Noise and Vibration
I sailed a 470 when it came out. It's been isolated and insulated from the hull. Just goes to show you that they can do it right if they want to.
Ron Marcuse C400 #74 "Good Vibrations", CaptRon400@aol.com

Subj: RE: [cat] Engine Noise and Vibration
Did you install new motor mounts, if so, whose were they?
John Cairns, C-28, #194, "TALISMAN", jcairns2@visteon.com

Subj: Re: [cat] Engine Noise and Vibration
No, I have the original mounts. I am going to install a flexible shaft coupling. I made that modification on my 31' Benetau with a 2 cyl Volvo and the hull-coupled noise went down significantly.
Gary, Gcooper288@cs.com

Subj: Re: [cat] Engine Noise and Vibration
I was looking at engine installation on my friend's Hunter (very quiet for those just joining this thread) and there's nothing unusual about it. The soundproofing doesn't look any different than the sound proofing on my C34 (although there's more space around the engine, if that matters), normal looking engine mounts, no flexible coupler for the shaft. It does have a PSS shaft seal, but that's not normally touted as a noise reducer. Maybe the Yanmar is just a quiet engine or there's something inherently solid about the Hunter structure?
Bob, C34 #1290, rgreenhaus@omnisky.net

Subj: Re: [cat] Engine Noise and Vibration
Are we talking about noise or vibration? Both can be defeated.
Additional insulation around the engine box, exhaust system, and an external breathing system would really tend to quite these things down. Some of the sound is directly related to the vibrations (the "echo" effect of having the structure shake). Imagine if your car's firewall wasn't insulated, had a much smaller exhaust that terminated near where people sat, and it breathed fresh air from somewhere inside the passenger compartment.
Eliminating vibration is just a matter of isolating the engine and shaft from the main structure of the boat. I don't think that ANY 4 (or less) cylinder diesel is vibration free. But some are obviously better than others. Take a look at the engine mounts on a good automobile - these are not simple devices. The rubber sandwich does not really connect the two steel sides (remember all of the GM failures about 15 years ago), but isolates the steel coming through it from carrying the vibration. These things are tuned to eliminate primary and secondary harmonics even. It's a science.
Are there any 470's on this list? I'd be curious as to what Catalina did differently. I've got one on my dock, and I'll ask him to let me take a look in a few days.
Ron Marcuse, C400 #74, "Good Vibrations", CaptRon400@aol.com

Important: The opinions expressed here are those of the individual contributors to this page, and not those of the Catalina 34 National Association or Catalina Yachts, Inc. Additionally, this material has not been reviewed by Catalina Yachts, Inc. for technical accuracy. This page's maintainer cannot guarantee the accuracy of this information or the desirability of suggested modifications or upgrades. Please obtain assistance from a competent marine mechanic or boatyard prior to making any significant modifications to your vessel.   

 

 

Last modified by Phil Imhof, Wednesday, August 11, 2004 . Copyright © 2001 by Catalina 34 International Association.  All rights reserved.