Engine Soundproofing

[senorquill]

Good morning,

The old sound proofing in my engine compartment has dried up and started to just fall apart.  Does anybody have good advise on a new product to use and thickness?  Does it need to be Marine Grade, which is far more expensive. 

Thanks,

Ryan

1987 C34 (Hull 368)
Engine: Universal M25XP

[scgunner]

Ryan,

Same thing happened to me, my boat is about the same age as yours, the foam started crumbling and basically turned to sand. I did a replacement a couple of years ago, it wasn't that difficult. I went to my local marine chandlery and was able to find sheets of the exact same material and in stock, I think it's pretty standard stuff and it wasn't that expensive.

[Ron Hill]

Guys : I wrote an Mainsheet tech note article w/pictures when I replaced my sound insolation.
Great articles /idea in those Mainsheet tech notes!!   

A thought

[Jon W]

Same thing happened to me. I removed all of the old, and replaced with Sundown Sound Noise Reduction Kit that I purchased from Defender.com. They had a 1" thick version and a 1/2" thick version. I used the 1/2" thick version. I've been very happy with much reduced engine noise.

Several on this forum used the 1" thick version and thinned it out to fit around the pulleys, alternator, etc.. I've not heard anyone explain how they sealed the giant hole above the transmission and HX where the engine compartment opens up under the aft cabin. At least on a MK1. I keep intending to seal that hole, but still haven't 5 years later. 

FWIW - Think of sound as water. It can be blocked, but will redirect and flow through any hole, or transmit thru thinner sections regardless of how thick the sound insulation is in most places. In other words, the sound attenuation is only as good as the weakest/thinnest section.

[Ron Hill]

Guys : I used 1 1/4" thick sound proofing.  The thicker the better, but I did the job when the engine was out for repair!!

A thought

[Jon W]

1 1/4" isn't going to fit in a 1987 engine compartment without making pan downs to ~ 1/2" thick to avoid interfering with for example the engine pulley's, and alternator while closed up to run or opening up for service. I suspect it will also interfere with the top of the engine, but would need to look. How did you sound proof/seal around the HX, bell housing/transmission, control cables, hoses, and the large opening at the back of the engine compartment?

[Noah]

1-1/2 in would NOT fit in my 1990 either. I used 1 in. Soundown from Defender and in some areas 1/2 in. West Marine knock-off (which had sticky back). Where I ran out of 1 in. and needed it, I doubled-up two layers of 1/2 in.
https://c34.org/bbs/index.php/topic,10340.msg79906.html#msg79906

[ewengstrom]

I did mine this past winter when the engine was out and did do up above the transmission and exhaust riser. I'm not sure that would have been possible with the motor in place...although you COULD lay on your back upside down thru the access hole in the aft cabin (you'd have to get REAL cozy with the transmission) and access the area that way....talk about "boat yoga"!!!!!
I did have to adjust the thickness around the crankshaft, water pump pulley, thermostat housing and exhaust riser but using screws with larger washers to reduce the thickness has worked well and I'm VERY happy with how quiet the beast is now.

[Ron Hill]

Guys : Let me give you a heads-up when adding insolation. 
Make sure that you have "rubber" boot protection on the positive connectors, especially the water temp.  If the metallic covering touches a bare connector you'll get a false reading/short.

A thought

[Dark n Stormy]

I used the "Sailor Solutions" product.  This is the only pic I seem to have...

[Noah]

Looks interesting and clean. Why did you decide to not tape seams? Also, what is your boat and engine model/year/hull number?

[ewengstrom]

I used the "Sailor Solutions" product.  This is the only pic I seem to have...

That's the material I used and I'm very happy with it. I believe it took 15 tiles to do the entire engine compartment on a MK 1, that includes the area over and behind the transmission and exhaust riser.
No issues so far.

[Dark n Stormy]

Sorry, it took me so much time to attach the photo I ran out of time and I skimped on the text. 

I did end up taping the seams in the end and I did put more small pieces around the edges.  I used aluminum duct tape for the seams.  I cleaned up any oil with acetone and stuck the pieces directly to to the wood no screws needed so far.   

The engine is now a lot quieter...

I have a 1997 MkII boat with the M35AC engine and I can't remember the hull number. 

all the extra wires and terminals are for the powered winches (bad choice of location in my opinion) 

Brent   

[senorquill]

All,
Thanks for the advice.  I ended up getting Soundown Yachtsman's Jr. Noise Reduction Kit from Defender.  It's half inch, but says it has the same DB reduction as the slightly cheaper 1".  I only have the port side with the rotten sound proofing, so I'm sure this will be a significant improvement.

Ryan