The noisy 4D61 rides again

[Sprig1]

Vic what was different and how did they do it.

[rnummi]

Sound proofed engine compartment hatches complete. 1 Layer Dynamat Extreme and 3/4 inch Dynamat Hood-liner. We shall see.

[Vic K]

Chris,

Every surface was covered with sound proofing then all the engine equipment was installed. The ideal set up. Did make a big difference. I was very impressed. It was an 84 and what the owner said he's had the boat ten years and it was like that when it was bought.
This is the way it should be done.

Vic

[Sprig1]

Vic how did they hang everything? Did they put another bilk head out in front?

[rnummi]

The engine room bulkhead requires sound deadening according to Dynamat Rep. Without some sort of material absorbing vibration you get harmonic vibration transmitting through the fiberglass (which acts like the outer surface of a bass drum). For all intents and purposes, the untreated verticals act like a sound transmitter. This is why you can hear the music outside of an untreated car.... I was pretty impressed with the difference between a treated and untreated car at their shop. According to the boys..... Makes no difference whether it's interior or exterior mounted (I.e. Engine room bulkhead). It's essentially a vast piece of butyl (yep) tape with an aluminum facing. Sticks to anything. He indicated it doesn't matter who makes it... As long as it eliminates the resonance. I read reviews for different brands... All are essentially similar in what they do. Eliminate harmonic vibration and reflect heat.

I'm following your lead of pulling the equipment off one bulkhead at a time, cleaning, painting. I've been to a rolling boom box factory, it apparently works. I'll mount it, then remount equipment. Will report back as to efficacy on A27.

[Vic K]

Chris,

I assumed it was adhesive. No battens that I could see. I understand the self adhesive stuff is real good. So much so that you best put it on correctly the first time.

If your engine compartment is clean and empty I would do it the right way and never look back.

Vic

[Sprig1]

Hi Vic what I was wondering was how all the hot and cold water lines,electric wires,fuel filters attached to the bulk heads. Where they still through bolted? It would seem that would defeat the purpose if they where.

[Vic K]

Chris,
Sorry I didn't notice of how things were hung. I would imagine you could use a screw and bracket to attach items. If I get a chance I'll look again.
Vic

[Beta Don]

Vic,

So you're back to using your original movers blanket treated with fire retardant and that works almost as well as the heavy blanket you bought later on? I have no idea how loud my Yanmar is compared to the 4D61 since I never heard mine run before I yanked it - I assume it's already a good bit quieter because it's turbocharged and I know that makes a big difference in both the intake and exhaust noises . . . . but of course it could be quieter still and that would be nice. We can converse in normal voices and the VHF is usable, though I have it mounted in an overhead console so it's pretty close to my ears. I'd like to try your blanket idea and see how much difference it makes for me

Don

[Vic K]

Don,

I think you'll be happy with it ( I used three) . The cost is less than $40 if you include the retardant. I understand that turbos like the Yanmar have a high pitch 'whine'. The 'blanket' did change the pitch of the 4d61 to one that's in the lower end and easier on the ear. Anxious to hear how it turns out.

Vic

PS: When folded the blankets fit perfectly over the 4D61 so I stitched them to stay that shape. Made it easier to handle. I can check oil, water and belt tension with not having to remove the covers.

[Beta Don]

Vic,

What RPM do you use for cruise speed? With my Yanmar I'm running 2200 to 2300 most of the time

I'm guessing you bought 72 X 80 blankets?

I noticed that Harbor Freight sells a 6/ by 8' fiberglass welding blanket. I'm wondering if this would further reduce noise if used in combination with a couple of the movers blankets - Using one closest to the engine would certainly reduce the (remote) possibility of fire

Don

[Vic K]

Don,

Running about 2150 puts me right at hull speed. Wind and tide affects this of course. Give some thought to the placement of the receivers for the 'blanket' support rods so they are easy to remove. I used some aluminum tubing from an old bimini frame. I did wrap the exhaust elbow as that was the main source of heat. My 'blanket' doesn't rest on any part of the engine. Also I did relocate the air breather to an area on the bulkhead to make sure the engine was getting good air.

This is such an easy fix you can experiment. I wasted over $200 bucks on the sound proofing blanket I bought on Ebay. The cost plus having it cut to fit the engine. Now it's setting in the barn gathering dust. If anyone wants to buy it I'll be glad to make 'em a deal.

Again I think you'll like this approach.

Vic

[rnummi]

Vic, how's the engine noise in aft cabin? Do you have the bulkheads in place (i.e. Evidently I'm missing a "foot" bullhead in aft cabin) mines open all way to engine compartment aft bulkhead.

[sail149]

The bulkheads vary. There is no standard on how the bulkhead should be , except the solid engine bulkhead.
Some block off the lockers from aft cabin some don't!

[Beta Don]

I'm guessing the early boats didn't have any bulkheads aft of the engine room bulkhead. Mine didn't anyway. In some ways it's a plus as you can easily crawl forward into the lazarrette from the aft cabin

Vic did away with the aft cabin completely and extended the floor aft, so no worries (for him) about engine noise in the aft cabin

Don