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Go Back   SailNet Community > General Interest Forums > Gear & Maintenance
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  #21  
Old 02-08-2007
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I've seen more boats have problems due to water cooling issues, and don't really see the need to risk it on a boat that is already having some issues. If the engine continues to run, you can run as many large electric bilge pumps as you need...but as soon as the engine fails... you're down to your batteries and whatever manual bilge pumps you have...

It is really a personal choice, but I think that having a small bilge pump for the day-to-day stuff, and one or two large bilge pumps for emergency use, that have a higher float switch than the day-to-day pump does makes far more sense. As long as you have diesel and can keep the motor running, you'll have electricity to keep the pumps going. If you use the raw-water cooling as part of the pumping solution and it gets blocked with crud... then you're down a pump, but also have lost most of your electrical generation capacity, and possibly the ability to move your boat toward safety...since the diesel is also powering the prop...

A small hole in the bottom of a boat, say 3' below the waterline because of a grounding, even if it is only an 2" in diameter will let in 136 GPM... Given that most bilge pumps are rated at GPH, not GPM, the largest 12V bilge pump I've been able to spec out rates at 3000 GPH, or 50GPM, which would require three of them to stay ahead of a small 2" hole. That is an optimistic estimate as well, since the pumps are rated at 0' of head, and in this case, we'd have at least 3' of head, to get the water out of the bilge and up past the waterline. I don't believe a raw water cooling system runs at 50 GPM, given the small diameter of most of the tubing and passages in it.
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  #22  
Old 02-08-2007
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Quote:
Originally Posted by Razman23
Im not going to get into the pump debate already going but I would like to suggest that instead of connecting the bilge pump hose to the emergency hand pump hose, you may look at teeing it into the hose from your cockpit scoopers. I dont see any sense in putting ANOTHER hole (granted its has a seacock) below the waterline of your hull if not needed.
Raz- You have to be really carefull with this aproach as it is possible for water from cockpit to backflow down into the bilge.
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  #23  
Old 02-08-2007
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SD - I see the engine pump as additional capability. Clearly, choose your pumping capacity and there is always a little bigger hole below the water line that will overcome it. In such circumatances the pumps are just winning time while one struggles to patch or bung the hole.
Yes, crud can stop any pump, but that applies to the electric ones too, so strum boxes are needed with a mesh that only allows acceptable sized dirt through. Since the raw water pump already has a strainer, adding a strum box to the "emergency inlet" plus a Y-valve is a fairly competitive way of increasing the time before the life raft starts looking attractive.
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Old 02-08-2007
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Quote:
Originally Posted by T34C
Raz- You have to be really carefull with this aproach as it is possible for water from cockpit to backflow down into the bilge.
Ah crap! Youre right.....................nevermind.
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