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Discussion Starter #1 (Edited)
Older yanmar 12 hp, 1970s. I am trying to figure out the purpose of these additional lines on the water pump. One outflow line ties into the bilge line outflow. Another outflow line runs to the bilge pump compartment. This line by the bilge pump looks like it was connected to something at one point and has been severed. The source of the additional inlet is a mystery. Two strange things happen in this system. First, when the bilge pump is running, water flows out of the line in the bilge pump compartment. This makes some sense because the water is likely coming out of the bilge line, going through the pump and through the other additional outflow line and back to the bilge compartment. Water also flows out of this line when the engine is running. I don't like the idea of water filling up the bilge compartment when the engine is running.



Is this normal to have multiple outlets on the water pump? I am thinking it is some sort of improvised way to pump water for the sink/bathroom, or as a backup bilge pump that runs off the engine. I know very little about the vessel's plumbing or about marine plumbing in general. Any help is greatly appreciated. Thank you!

Rob
 

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I have seen this done for:

pressure heated water
refrigeration

im not understanding the bilge pump scenario unless it means you unhook the pickup to use as an emergency pump but then the engine might suffer damage if the bilge runs dry

dont know

its not uncommon to use the engines to pump water throughou the boat

another scenario is running a bilge keeler(edit I mean keel cooler using tubing outside to cool water) sorry

does your boat have a bunch of tubing inside or outside the hull?
 
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Its common on larger powerboats to have the ability to use the engine pumps as emergency bilge pumps. Perhaps the PO picked up on that and connected his engine raw water pump up that way.
 

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Discussion Starter #4
Thank you for the responses! It is helpful to know that it is not uncommon to use the engine for pumping water for various uses. I suspect the loose line in the bilge was at one point connected to something, maybe the bilge pump. The old pump has been replaced with a more simple pump. Perhaps the problem is a missing one-way valve. It seems like a strange configuration:

 

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that looks like a 70's y series engine. They had an optional bilge pump which piggy backed off the raw water pump. I have a ysm 12. there are several good manuals on line, for free. Drop me a pm and I can email them to you.

Lou


i hav
 

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Just guessing here...but this arrangement would seem to be useful for de-watering the bilge using the engine raw water pump...using the raw water pump directly overboard through the upper discharge piping or directed to the bilge sump where the bilge pump would then be used to pump the bilge water overboard.

But it needs some valves in the lines shown in your drawing.
- a valve in the bilge suction piping to the raw water pump
- a valve in the raw water pump discharge directly overboard
- a valve in the raw water pump discharge to the bilge sump
- and a valve in the bilge pump discharge to prevent back flow through the bilge pump when the raw water pump is discharging directly overboard.
 
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