I generally agree with Ann-Marie, as usual. I have 19 openings in the hull below the waterline yet do not consider them to be a clear and present danger.
They all use Wilcox bronze flanged seacocks bolted to the hull, bedded in 5200, and fitted with stainless grease fittings for annual servicing. Two are in the forepeak, separated by a watertight bulkhead so any leaks don't matter. Some are always closed and have been seldom used in the life of the boat, several are always open. There is one that is used for two machines, the watermaker sea suction and the genset sea suction. So far I have had no trouble with this arrangement. However, I do agree with Ann-Marie in general that each machine should have separate systems, independent from other machines. But I do believe that if you have a large enough sea suction, say 2", and an equally large strainer, it would be possible to run several suctions from one seacock without problems. As for sinking the boat from seawater plumbing failure, any plumbing that is below the waterline, especially clamped rubber hoses, is a possible source of water for sinking, REGARDLESS of the number of sea cocks. Spiral clamps are vulnerable, I have had a failure or two here. Buy good ones, all 316 stainless (I have had 304 stainless rust and fail) and double clamp wherever possible. In the real world, in my own experience, the most prevalent water intrusions have been dock water with a failed fresh water hose fitting or hose, and propeller shaft packing gland (stuffing box) combined with inadequate or failed bilge pump. A failed coupling hose, torn or adrift from its nipples, on a "dripless" propeller seal seems to be fairly common. Two hefty bilge pumps with one switch higher than the other, with an alarm on the higher pump, is a Good Thing. Plumbing in place to switch main engine seawater suction from the seacock to a well-strainered bilge suction is also a Good Thing. I personally saved a neighbors boat underway by closing the engine suction seacock, pulling the hose off and by holding my fingers over the hose opening for a strainer sucked the bilge enough to make it to safe harbor. The biggest "sharing" problem I have is using the genset when the main engine is running. I have an unusual main, a Detroit Diesel, which has a high flow circulating style fuel system using 1/2" pipe. Most main engines have a fuel flow just a smidgen more than fuel consumption so it usually is not a problem. If I try to use my genset with the main running above 1100 rpm, the genset starves and shuts down. I wish I had built two separate fuel systems, but since it is just an inconvenience at this point I am not going to do it now. And one more thing, I would not install any seacock smaller than 1 1/2". I did at first have one or two 1", but after a few seasons I changed them out for 1 1/2". I have several 2" for main engine use. While a smaller opening seems fine when it is new, after a few oysters and barnacles take up residence, along with their gardens, the passage becomes much smaller. Norm S/V Bandersnatch Lying Julington Creek FL 30 07.72N 081 38.4W > [Original Message] > From: <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]>; TWL2: <[EMAIL PROTECTED]> > Date: 2/11/2008 10:23:40 AM > Subject: (T&T: & TWL2:) Re: & TWL2:) Cooling the GenSet and AC > > > My experience says all those options are going to give you problems except > perhaps for the Tee with valves but I don't like the limitation of not being > able to run engine and genset simultaneously. You will also forget to > change it over and have your engine fail in an emergency when you had to > start in a hurry and forgot to change over. > > Running in parallel from a pump output is a pressure balancing nightmare. > The flows required by the AC, Genset, and main engine are all going to be > different so no matter how you plumb in parallel you are going to need > "metering" valves so you can divide the flow so each item gets the correct > amount. This is a nightmare to set and keep set. You are working more or > less blind while adjusting the valve(s) and a small change in one will upset > the other. > > Running in parallel from the raw intake with separate pumps is a little > easier but again you can run into difficulties. If you get a blockage in > the inlet or strainer the suction pumps fight against each other. If they > are impeller pumps they will self destruct. If they are centrifugal, the > stronger one will suck water backwards through the other and whatever item > it was cooling putting them in de facto series. I ran two A/C units off the > one raw water intake and it was a nightmare with check valves to make sure > flow didn't get reversed if you turned one A/C (and its associated pump) > off. > > Running in series with slightly warmed water sounds OK in theory but again > your flow will be restricted to the smaller of the two in series and that > will be insufficient for the other one. > > Bite the bullet and add another raw water intake. Having been this route I > can tell you that it will be the easiest and safest in the long run. > Compared to the extra plumbing, hoses and valves that the alternatives need > it will probably be safer. KISS. > > I counted all the holes through the hull on our boat one time, including > EVERYTHING like electrodes, shafts, deck drains, hawser pipes etc. On our > 71 ft motorsailer there were close to 50 holes in the hull. > > Regards, > > Ann-Marie Foster, > [EMAIL PROTECTED] > > > ----- Original Message ----- > From: "Jim Isbell, W5JAI" <[EMAIL PROTECTED]> > To: "TWL2" <[EMAIL PROTECTED]> > Sent: Sunday, February 10, 2008 8:55 PM > Subject: (T&T: & TWL2:) Cooling the GenSet and AC > > > > > > I am installing a 4.5KW genset into my Gulfstar 36. At present there > > are two holes in the hull below the waterline. I like it that way. > > Holes in the bottom are what sink boats and the fewer you have the > > better. One of the below waterline throughhulls is the intake for the > > engine cooling. The other is the intake for the AC cooling. I dont > > want to have to cut ANOTHER hole in the bottom of my boat. > > > > When I install the GenSet I will need salt water for cooling. I dont > > want to take water from a manifold that is also connected to the main > > engine because if there is a leak in the hose to the genset then the > > engine could suck air and over heat. Yes, I could put in valving to > > run only one at a time since they will never be used simultaneously, > > but that would involve entering the engine room to switch back and > > forth with the obvious possibility of forgetting to switch it one time > > or another. > > > > I am thinking however that if I place a "T" in the line between the > > raw water pump and the AC, this is a pressure line, not a vacuum line > > so any leak could be wet, but not catastrophic. The "T" could feed > > the AC as well as the GenSet. Generally both would be on at the same > > time...since this is,.... after all, the reason the wife insisted on a > > GenSet....#8-) > > > > Another possibility would be to run the output from the genset to the > > AC. The temperature rise of the raw water is not great and so the > > water should still be cool enough to cool the AC coils. Or I could > > put them in series the other way around as I dont think the AC raw > > water output is that warm either. But it would seem more prudent to > > cool the GenSet FIRST since the AC would not be damaged by a lack of > > cooling, just inefficient. > > > > Any comments on these ideas????? > > > > > > > > -- > > Jim Isbell > > "If you are not living on the edge, well then, > > you are just taking up too much space." > > > > > > > > --~--~---------~--~----~------------~-------~--~----~ > To UNSUBSCRIBE or change your email from live to digest or web board only, please send a request to Andina at [EMAIL PROTECTED] > POST messages in an email to [EMAIL PROTECTED] > View the live board at http://www.yandina.com/TWL2 > -~----------~----~----~----~------~----~------~--~--- _______________________________________________ Liveaboard mailing list [email protected] To adjust your membership settings over the web http://www.liveaboardnow.org/mailman/listinfo/liveaboard To subscribe send an email to [EMAIL PROTECTED] To unsubscribe send an email to [EMAIL PROTECTED] The archives are at http://www.liveaboardnow.org/pipermail/liveaboard/ To search the archives http://www.mail-archive.com/[email protected] The Mailman Users Guide can be found here http://www.gnu.org/software/mailman/mailman-member/index.html
