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
Catalina’s? 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
Catalina’s 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 -- it’s very quiet and smooth. Only the
sound of the splashing exhaust water signals that it’s
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
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reviewed by Catalina Yachts, Inc. for technical accuracy. This
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information or the desirability of suggested modifications or
upgrades. Please obtain assistance from a competent marine
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