4 Out of 5 Boats Sink at the Dock

JimK · Post by **JimK** » Fri Apr 27, 2012 12:38 pm

Hi folks,

I am reading Sorensen's Guide to Powerboats. It's well written and loaded with useful information. One item in particular struck me and I was curious about the forum's thoughts. In the discussion on dewatering there is a chart with the rate of flow of water into a boat based on the size of the hole and the depth to which the hole is under water. For example a 1/2" hole six inches below the water line flows at 4GPM and the same hole 36" below the water line flows at 18GPM. A 6" hole flows at 500GPM and 1,250GPM at the respective depths mentioned in the previous example. The book has a table with more data but the examples give you an idea of the range.

Given that most bilge pumps are rated in GPH (not GPM) a 1000GPH pump translates to 17GPM. You would not need much of a hole in your hull to have water flowing in at a rate greater than most bilge pumps can handle. The book mentions a Y-valve through hull fitting that would allow you to divert the raw water intake into the bilge allowing you to run your engine as a bilge pump. This sounds like a worthy idea for virtually every boat with an inboard engine. Until reading this book, I never heard of this type of valve. Is anyone on the forum familiar with this type of setup and has anyone ever seen one on a boat?

Thanks,
Jim

rossjo · Post by **rossjo** » Fri Apr 27, 2012 12:47 pm

There are several people on here with these "crash valves" ... its on my list, but not done yet.

JimK · Post by **JimK** » Fri Apr 27, 2012 12:58 pm

Do most folks put one on each engine in a twin engine setup?

jordan · Post by **jordan** » Fri Apr 27, 2012 1:19 pm

It's on my " to do list". I'm going to do both engines just in case! Figure if I should ever puncture the hull I'll be able to pump a lot of water.

Stripermann2 · Post by **Stripermann2** » Fri Apr 27, 2012 1:20 pm

I bought this book a few years back. A good refresher from time to time on the reality of disasters. You can get online of course or at bookstores. You can flip through the second link and read some archived stories too.

http://www.boatus.com/seaworthy/book.asp

http://www.boatus.com/seaworthy/default.asp

rossjo · Post by **rossjo** » Fri Apr 27, 2012 3:17 pm

All of the bigger sporties I've been on have a set of crash-valves on each engine.

Friend's pair of 900HP Lugger diesels have about a 3" to 4" pipe, so they will really suck some water up!

prowlersfish · Post by **prowlersfish** » Fri Apr 27, 2012 5:59 pm

Good discussion . Crash valves are a good thing to have . However the title to you post is " 4 Out of 5 Boats Sink at the Dock " very true and I will bet 99% of them the owner was no ware around so crash valves would be of no use . But hit something under way the could be a nice thing to have as long as the hole is not to big . I had to deal with a 4" x 5" hole a few years back , Crash valves may have been nice but would not have been enough in I took the time to open them.

Having a way to stop a leak should be part of your emergency plan . And you should have one if not a writen plan , something planed out in your mind . Think about what you you would do if the worst happens and be ready if it happens . I have been down that road and am happy to say boat and crew are fine

trojanmanXS · Post by **trojanmanXS** » Fri Apr 27, 2012 6:04 pm

At what my insurance guy charges I'll cut the dock line and push her out and make it his problem

Muskokan345 · Post by **Muskokan345** » Fri Apr 27, 2012 7:23 pm

Dont forget, as more water enters the boat, the further down that hole becomes, therefore exponentially increasing water flow into the boat. Havong said that, I dont care how much I pay in insurance, I'd rather have my baby safe and sound, and do everything I could to save her!

prowlersfish · Post by **prowlersfish** » Fri Apr 27, 2012 8:17 pm

X2 I agree
And Its not only saving the Boat it could be saving your life and of course any one else on board .

k9th · Post by **k9th** » Fri Apr 27, 2012 8:25 pm

Great discussion. First I have heard of crash valves but they sound like something I need to get installed.

jefflaw35 · Post by **jefflaw35** » Fri Apr 27, 2012 10:46 pm

k9th wrote:Great discussion. First I have heard of crash valves but they sound like something I need to get installed.

+1

The Dog House · Post by **The Dog House** » Fri Apr 27, 2012 10:51 pm

The seacock for the engine water intake on my boat has a fitting that can be used to hook it up to a garden hose. It's very handy for running the boat on the trailer. I also keep a short piece of garden hose onboard I can hook up to it to use as a crash valve. A Chrysler 318 is a great bilge pump!

Big D · Post by **Big D** » Fri Apr 27, 2012 11:11 pm

Touched base on this topic in http://www.trojanboats.net/wforum/viewt ... c&start=15

Dog House, though you have the right idea, I have a bit of an issue with your particular set up as described for this particular purpose. A garden hose is made for pushing water through and may collapse in a suction application. Further, a typical garden hose at half inch or 5/8 is an insufficient ID and will starve the pump at anything over idle. I suspect reving her up will certaily collapse that small a hose. The best set up is using a valve that is fully ported to the size of the original intake hose to ensure maximum pumping capacity in an emergency. Something to think about.

Allen Sr · Post by **Allen Sr** » Sat Apr 28, 2012 6:55 am

Big D wrote:Touched base on this topic in http://www.trojanboats.net/wforum/viewt ... c&start=15

Dog House, though you have the right idea, I have a bit of an issue with your particular set up as described for this particular purpose. A garden hose is made for pushing water through and may collapse in a suction application. Further, a typical garden hose at half inch or 5/8 is an insufficient ID and will starve the pump at anything over idle. I suspect reving her up will certaily collapse that small a hose. The best set up is using a valve that is fully ported to the size of the original intake hose to ensure maximum pumping capacity in an emergency. Something to think about.

x2 I agree, needs to be same size as the plumbed intake not smaller.