The noisy 4D61 rides again

[Vic K]

FYI: I had a sound blanket custom cut to fit my 4D61 it worked but it was heavy and not easily removed for engine service. I replaced it with cargo blankets ( sprayed with a fire retardant). They work as well as the sound 'blanket'. These go over two rods that are mounted on each side of the engine( photo earlier in this thread). It's very easy to check oil, coolant etc. The engine sound has gone down in volume but most important, I think, is that the engine sound changed to a lower pitch. Now at cruise you can carry on a conservationist in a normal tone as well as hear the VHF. Early on in this process I had the engine mounts replaced twice. The first time the mounts were, I was told, too hard, and helped cause a harmonic vibration. The second set was the same as comes with the new Beta diesel. I'm very pleased. Hopes this helps.

Vic

[rnummi]

How bout under the engine hatches? Still factory foam or did you change it out?

[Vic K]

Yes I replaced the insulation under the engine deck places before doing anything else.
Vic

[rnummi]

Where did you get new insulation for under Engine hatches and what was it? How did you attach it? Contact cement?

[Vic K]

It was given to me. A soft, foil covered material that looked like the stuff you put around water heaters. Used spray adhesives and wood battens that screwed to the inside of the hatch.

[rnummi]

Anyone ever use dynamat. Supposed to be the cat's pajamas. Look at thir web site... Three layers of sound deadening hood liner should do the trick methinks. If it's good for the rolling boom boxes it's good enough for me. Initially I went to Advance Auto to buy "hood liner" the guy looks at me like I'm nuts.... He says order from JC Whitney.... Yeah right.

[JT48348]

Good idea. I have not. I don't know anything about that so really can't comment. But if I did know something about it I would definitely offer to help. I Know something about other things. But I'm not sure if they apply.

How about ear plugs? Or loud music?

I think I have some technical acoustic information over on the thread about pilothouse fixes. Not sure which one. But you can search through them all and I'm sure it's there.

[rnummi]

I like the earplugs idea personally. That being said the horn from the freighter as it hits you like PT-109 would be a little difficult to hear.

[rnummi]

New dynamat hoodliner arriving today....installation on engine access panels scheduled for this weekend. I read (in the "how to make your small vehicle incredibly obnoxious by installing a concert hall stereo" monthly) where it is critical that all surfaces capable of resonation be covered or addressed. I noticed in Don's pics that the vertical surfaces in the engine compartment weren't covered or soundproofed.... How do most folks address this issue? I realize that this is a subjective issue but has anyone gone "the whole none yards" like Vic and done the entire engine compartment (including his incredible blanket)?

[Vic K]

FYI: I haven't done the whole engine compartment. Can't get to many surfaces because of equipment, hoses, panels etc. Whats helped my situation is the new engine mounts and the sound blanket. I also installed a carpet with a liner. I'm quite happy with the results and don't plan to do more.
Vic

[rnummi]

Well the new Dynamat Hood Liner got here. Doesn't look as thick as the original though. Did you use aluminum. Tape to seal edges?

[rnummi]

Woohoo, the Dynamat Extreme just showed up too. Per their web site, Dynamat Extreme first, overlaid with the Hoodliner. At least the darn engine hatches will be done. Interestingly enough, the Dynamat extreme indicates that the primary "sound absorption, vibration damper is sheets of butyl overlaid w aluminum". I shall report on the Db level increase/decrease one way or the other.

[sail149]

Hi
I looked at a very late model '93 with a 180 hp Merccruiser 6 cyl , a rebadged BMW , but actually Italian engine!
Anyway the factory installed some padding on the FWD and aft firewalls before mounting any accosories. They also added a soft liner under the 'pilot house' roof ( for reflected sound I assume.). My point is the sound deadening has to be well thought out from the start. Retrofitting will be a compromise at best.
There are lots of things that need to be done right and there is no magic bullet.
Some simple things, no direct air path out of engine compartment , use lots of corners to bend the air/ sound.
Don't have metal fastness that go thru from the engine compartment to the out side like the cover hinge bolts.
Engine mounts , must be matched ( see what Vic said)
Don't use fiberglass engine beds, the transmit noise to the hull, hence the need for wood in engine beds with the rot problems.
By the way the 4D61 uses gears for the timing instead of a chain. It's incredibly reliable and long lasting .....but heavy and noisy ...which is most important?
Good luck with the noise issue, Vic's blanket is remarkably clever and simple......

[Vic K]

Warren,

FYI: I was informed that some of the noise from a diesel comes from the air intake. I relocated the air filter via a hose to the bulkhead. This moves it from under the blanket so it's not taking in hot air. I was also informed that diverting the air flow from a straight line to angles would also help. So far there hasn't been any down side to these changes.
I never liked the air intake being close to the heat exchanger. Just in case there was ever a leak on that side of heat exchanger water could be sucked into the engine. Which I understand wouldn't be a good idea.

Vic

[Sprig1]

I was going to fill the cracks and holes along the bulkhead with sound deadening foam. One place no one has addressed is up the sides of the pilot house I don't know if it makes any difference or not. It is totally open. I was going to put aluminum clad Foam board in there and seal it with foam. It would seem that it would stop the sound from traveling up and around you. Any thoughts.