3.0 Volume

[Sliver]

Hello all,

Finally had a chance to get my new/old boat on the water, 89 Sunbird 3 liter Cobra. I am coming from a 1981 Lund with 70hp Johnson outboard and was thinking that the I/O would be a smoother quieter ride. Well the OMC is smooth but once on plane quite loud. It looks like a live and learn lesson huh? I see from some posts that they did have a through the prop exhaust but mine is through the hull. Any remedies? It looks like everything is in place mechanically, it is very quiet at low speed with the top of the drive underwater, but once on plane the top is exposed and the volume goes up. So as always, thanks to you all.

 

[Howard Sterndrive]

Re: 3.0 Volume

you mean the exhaust bellows is missing? or someone actually installed a thru hull on a 3L - I can't imagine...

just buy and install the exhaust bellows and your exhaust will be mainly through the prop- a few slices in the bellows will let a tiny bit out above water

 

[wcasey5]

Re: 3.0 Volume

Mine is pretty quiet on plane, relatively speaking. I can't imagine letting that 1956 massey ferguson type sound loose with a through hull exhaust on a 3.0. Like stated above, sound's like the exhaust bellows is missing. Very easy fix that connects your outdrive hull exhaust exit with your propeller.

 

[Sliver]

Re: 3.0 Volume

Like I said I thought all looked good in the doghouse. I see from another post by bruceb58

"A ripped exhaust bellows won't make a difference in performance.

There are no exhaust bellows in the engine compartment. There is a small exhaust tube between the riser and the exhaust pipe going to the sterndrive though. If that is damaged, you would get exhaust and water in your engine compartment and fill your boat with CO."
So I am wondering.. am I missing something outside? I can't post a pix but found one that looks similar by memory. Is there something missing here?

 

[Bondo]

Re: 3.0 Volume

Like I said I thought all looked good in the doghouse. I see from another post by bruceb58

"A ripped exhaust bellows won't make a difference in performance.

There are no exhaust bellows in the engine compartment. There is a small exhaust tube between the riser and the exhaust pipe going to the sterndrive though. If that is damaged, you would get exhaust and water in your engine compartment and fill your boat with CO."
So I am wondering.. am I missing something outside? I can't post a pix but found one that looks similar by memory. Is there something missing here?

Ayuh,.... Outside the boat, Under the drive is where the exhaust bellows lives,...

 

[Sliver]

Re: 3.0 Volume

Bond-o,

Appologies for my ignorance, like I said this is my first I/O. I will take a look when I get home but I can't recall seeing anything flexible there... duh so that's the problem. Thanks.

 

[Sliver]

Re: 3.0 Volume

So I went home to look and was hpoing to find nothing but alas it is there and intact. I was hoping that the holes were wear but according to the parts place that had one they are supposed to be there. Maybe I had too high of expectations about the volume. Any other thoughts? Thanks again.

 

[Levinz11]

Re: 3.0 Volume

Running on plane at 25mph + is not going to be a "quiet" experience. You have an engine a few feet away turning 3000 rpm's, wind, water hitting the hull, your own giggles, etc all happening at once.

My buddy has a skiff with a 115 Johnny on it. Up on plane the sound to my ears is different but not much louder. I have been on newer boats that are quieter. I guess the doghouses are sealed better/differently.

You could line the engine cover with some kind of sound deadening material. I've seen threads on this.

 

[Sliver]

Re: 3.0 Volume

Thanks Levinz11,

Yeah I know what you are talking about and I was not expecting quiet, just maybe so I wouldn't have to yell to the person sitting next to me. Will just take some getting used to I guess. I will say that most of the sound is coming from the exhaust as I slid open the doghouse when we were running and not much from there. Thanks to all of you.

 

[Howard Sterndrive]

Re: 3.0 Volume

poor water flow through the exhaust manifold will make an i/o engine loud - the manifold will really resonate on some. If the manifold feels ok to the touch when underway, I guess you just need to review the doghouse design and insulation.

Boats with the sport seating (bench at the rear and sunpad over engine) tend to be way quieter than those with jumpseats either side of the doghouse.