How I made my M25XP quiet.

Aug 26, 2013
24
Catalina 30 MKII Horseshoe Bay
Aaron-- that was perfect, just what I needed to know. If I could have remembered oh to message you I would... I remember flipping the lid on my 70 el camino!
If I have time before I move, Im going to approach Coriolisbc and see if I could go out on his boat and on mine and do some sound meter tests at specified distances. He has heard mine and seemed very impressed with the sound reduction.
 

rmwac

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Apr 22, 2011
19
Catalina 30 Watkins Glen
Hi all: I bought the Kubota air intake assembly for the D850 diesel ($105.00 USD) last week. The hoses shown in Aaron's parts diagram are no longer made, so I made my own hose configuration by using three 90 degree, 1 1/2" Fernco rubber boots (Lowes or Home Depot, in the PVC plumbing aisle), and a 24" length of 1 1/2" PVC plumbing pipe. If you have a Cat 30 of the eighties vintage, there is plenty of room above the transmission in which to house the intake assembly. This DOES quiet the engine, but it is NOT dramatic IMO. The rushing sound of intake air is eliminated, but all the other loud engine-related rumbling continues. The stock air cleaner (with the steel wool and foam wrap) is worthless for eliminating the air intake noise, and the engine sounds no different with or without the stock air filter. With the Kubota filter unit, you WILL have a noticeable decrease in air intake noise, but not miraculous for overall quieting, at least not in my case. I'm now looking to new engine mounts and soundproofing to continue the quest. I just purchased some RAAMmat and Ensolite to line the settee enclosure with. I'm also considering creating a soundproofed "false wall" between the engine and the macerator pump area to eliminate some of the large cavity beneath the settee area. Any input on selecting appropriate mounts would be most appreciated. If anybody would like photos, I can provide them.
 
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rmwac

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Apr 22, 2011
19
Catalina 30 Watkins Glen
Aaron: which mounts did you use, and can the job be done without pulling the engine?? I've read a post or two describing how to replace one mount at a time "in situ," and am encouraged. Will any of the newer and softer mounts use the original mount holes, or will modification be needed? I'd like to buy the correct parts to minimize my agony the first time!
 
Nov 24, 2011
95
Catalina 30 San Diego
From the pics it looks to me that Aaron's engine compartment is already sound dampened so muffeling the intake would make a difference.
 
Sep 25, 2008
30
Catalina 30 Lake Murray Sailing Club
From the pics it looks to me that Aaron's engine compartment is already sound dampened so muffeling the intake would make a difference.


Greeting to all,

I have a 87 Catalina 30.

After reading all of this thread over the months, I purchased the Kubota air Intake and did a dry fit. Interestingly, the motor was a little quieter at 1000 RPMs and significantly quieter at 1800 RPMs and above. I will install it just right of the opening under the galley sink. I purchased 3" air intake hose from local diesel supply.

I have installed sound abatement panels to all fiberglass walls surrounding the engine as well as to the underside of the wooden access panels above the engine and macerator pump. I even surrounded the water muffler with the panels.

My mechanic and I also installed motor mounts with the boat in the water. We placed a brace under one side of the engine, removed and replaced mount then did other side. We adjusted the propeller shaft at Hurst transmission. There is a spot at acceleration (around 1200 to 1400 RPMs) where there is extreme vibration. We are still trying to figure it out as to further reduce vibration.

These three "fixes" were expensive and worth every penny. Approximate cost: $600. Once I go from dry fit to final install, I will post pictures.

Keep posting topics. I love the conversations and learn a lot!