Marine Head Inlet Seacock

[jlflynn1]

I am new to the Grady White forum, recently bought a 2009 Tournament 307 with 50 hours on her. (I had a Robalo R227 before, Four Winns before that and 1969 17" Tri-Hull as a kid growing up) The 307 was used on a fresh water lake and was kept high and dry in a boat house. Boat is very clean and is in good shape. I am going through the boat with a fine tooth comb, checking out every bilge hatch, trying to understand how this boat is constructed. The one major issue I am having is as follows:

I am getting this noise and vibration when I am underway at various speeds on plane, every time the boat hits a wave or goes up and down…. (Does not have to be rough out). The vibration almost sounds like when you put you turn your cell phone ringer off, and then the phone vibrates on the counter. I have narrowed it down to the marine head Inlet Sea Cock. (Although the vibration can be felt when you grab both the marine head inlet pipe AND holding tank discharge pipe) Yesterday I “opened” the marine head Inlet sea cock while we were underway at about 30 MPH and the noise / vibration 95% stopped. There was no change in the vibration/noise when I opened the holding tank discharge sea cock. So there is something going on with the marine head inlet Sea Cock. Any idea what is causing such a vibration while the sea cock is closed? Is it possible because this boat sat out of water for so long that some of the caulking dried out and the sea cock is vibrating on the hull? The head pump works fine too....water sucks in without a problem when the sea cock is open. Sea cocks do not appear to be leaking either. They seem a little damp from humidity and condensation but no leaking.
This vibration is a bit concerning…..I am not sure if I need to change the sea cock. Strange that when I “open” the seacock the noise stops……but when the seacock is closed I can hear the vibration while I am at the helm. Any thoughts or theories on why this is happening?

Greatly appreciated.

John

 

[Halfhitch]

John, It sounds to me like it is a harmonic vibration caused by the water slip stream passing a flush pipe end. Is your head seacock connected to a through hull with a scoop type intake or is it simply a through hull with a smooth opening? It makes me think of blowing across the end of a short pipe with the other end blocked(seacock closed) and it whistles. Then you blow across that same short pipe with the other end open(seacock open) and no whistle. What kind of pickup do you have?

 

[jlflynn1]

Thanks for the reply. I like the theory. No pick up strainer on these two sea cocks. See attached pic showing the two sea cocks for the head....looks like smooth opening.

 

[ROBERTH]

I have always noted a sound similar to what you describe on mine as well. Sometimes, it sounds like a whale call! Always chalked it up to the sound the thru hulls were making with the water rushing past them. Several years now and no issues found. Just the sound and not in all conditions do I hear it.

 

[Halfhitch]

Those pick-up tubes are far enough forward that they will experience moments of aeration and moments of running in solid water so I can see how they could trap air and then the fluctuations in water pressures while running could possible cause a harmonic "hammering effect on air trapped in one or the other tubes. A good test would be to plug them nice and smoothly and then see if the vibration goes away on your next outing.

 

[Ozz043]

Good pickup Halfhitch I like that theory

 

[Jonah]

Good pickup Halfhitch I like that theory

Ditto!

 

[jlflynn1]

Here is a quick video so you can hear the noise/vibration

https://youtu.be/7PJSxoPpwvc

I really want to figure out how to make this noise go away.
I was also thinking of removing the hoses. Thinking somehow they are contributing to the vibration.
Understand that while this noise is happening, I have reached down and grabbed the sea cock and can feel the vibration

 

[DennisG01]

You mentioned above that opening the seacock pretty much eliminates the noise. Why not run with the seacock open? If the real reason is as surmised above, then you're dealing with science and physics. Other than plugging the holes (which is not a feasible long-term solution, of course) or possibly tying the two seacocks together in some fashion - and possibly reinforcing them to the interior hull to eliminate the vibration - I'm not sure what else can be done.

I suppose you could experiment with wrapping them with some sound-deadening material. MLV sheets or what is used on the interior of car doors to deaden sound/vibration. I noticed that my '97 BMW has this stuff glued to the inside of the exterior sheet metal. Car stereo guys use this stuff sometimes when installing systems with more bass to keep the vibration/resonance to a minimum.

 

[jlflynn1]

Yeah maybe some pipe insulation to lessen the sound.

As for running with the sea cocks open.....I don't think that is recommended. Especially the marine inlet and the holding tank. A buddy of mine left his holding tank sea cock open on his Grady 283 and it filled up his holding tank. Not to mention, the hose is the weakest link for water to start pouring into the boat if their was a failure.

Just curious if anyone else out there runs with their sea cocks open? I'm willing to be opened minded and consider doing it.

 

[DennisG01]

All of the boats that I've ever owned with a head have had a fresh water flush, so I can't comment on that. But it seems that the valve at the toilet "should be" plenty to prevent water from seeping in. I have run with the overboard discharge seacock open and haven't had any issues. I don't know if it makes a difference, but mine have always been aft.

Edit: I want to clarify - the discharge seacock has ONLY been open when I've been well off shore. However, even that was only once or twice. I normally use the regular, deck pump out since I had also plumbed everything so I can do it at home (on the trailer), as well (into sewer)

 

[Legend]

My inlet for the head has always been open - no issues. The outlet is always closed.

 

[max366]

Another possibility is to remove the standard thru-hull and replace it with a strainer scoop thru-hull. Face the solid part forward and it should prevent the harmonics because the aft side will be open. Something like this

https://www.amazon.com/Bronze-Thru-Hull ... B001443JBS

It's a hassle to remove existing thru-hulls but in your case, it may be worth it.

 

[Halfhitch]

If you want to try that you could put a small clamshell on the leading edge of the hole, facing rearward. If the theory works then you could do the major change of the through-hull if you want.

 

[jlflynn1]

Thanks for the feedback guys. All good ideas. I'll figure something out next time I haul her....

 

[Ozz043]

I generally run with both seacocks open on my Marlin
I don’t see how it can can use an issue

Am I missing something? :hmm

 

[jlflynn1]

Update

Took boat for a 2 hour ride today. Pretty choppy out....the last 45 minutes of the trip, I opened up both sea cocks (inlet and outlet) ...no vibration/no noise. Which is great. I do not like hearing the vibration while operating the boat. So I guess I will be using the boat with both sea cocks open for now on and be sure to close them when I get back to port. Just surprised that no one else has complained about this or the engineers at Grady have not found a fix. I know it is “science” but still unacceptable in my eyes. I find it hard to believe a brand new 307 is running around with the same vibration. Down the road I might look into a fresh water head, and look to move the outlet to the back of the boat. (No one uses the mascerator anyway) and seal up the two current sea cocks.

 

[Legend]

Just a heads up - if you are running with the head outlet open, the holding tank and deodorizing agents can be drained by suction when running at high speeds.