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Discussion Starter #1
I am in the process of repowering my Hunter 27. It currently has a Renault engine which I will be replacing with a Yanmar 2GM engine. Yesterday I disconnected everything from the Renault engine in preparation of pulling it out of the boat. Let me prefice that there are two seacocks. One for inlet water and one (I thought) for outlet water. I noticed that only the inlet water cooling water line was connected to the engine. And the outlet water line ran somewhere else but was not connected to the engine. So I began to wonder what the outlet water line is connected to and what is the purpose of the outlet water line and its seacock?

The Yanmar 2GM engine that I will be installing is also a raw water cooled engine and I am wondering if it also will be connected the same way?

Could someone enlighten me with some understanding as to how this cooling system works and what I might need to pay attention to when installing the Yanmar engine? Thanks.
 

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I can't speak for sure on diesels but I know most raw water cooled gas engines expel the water through the exhaust manifolds. My gues on the other seacock is that it is an inlet for some other system.
 

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The cooling water probably goes from the engine to the waterlift muffler and then exits with the exhaust out the transom of the boat.

The other seacock may be for a salt water washdown system, a salt water galley faucet, the reverse cycle A/C system, transom salt water shower, or a watermaker if you have one.
 

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my 83 hunter 27 has the water intake right under the engine (yanmar 1gm) the only other thru hull in the area is the sink and its under the cockpit. i would think someone added one for something else, or maybe added a new one for a strainer instead of messing with the old thru hull
 

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On these engines the cooling water goes into a mixing elbow at the back of the exhaust manifold, then the exhaust and water go to the muffler after which it's expelled with the exhaust.

btw if this is a used engine you're installing it's worth checking the condition of that mixing elbow now. This is an area that is prone to corrosion and failure (esp if it's been in salt water)

If there's a line coming from your "extra" seacock, now's the time to figure out where it goes and what its for!
 

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It would also be worth re-bedding the through-hulls and making sure they're properly potted if you have a cored hull. :)
 

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Discussion Starter #10
I will be at the boat on Wednesday when the yard helps me pull the engine. I will take some pictures and post them.

At this point I realize that I didn't know much about the seacocks. When I purchased the boat, I was instructed to open these two seacocks prior to starting the engine and then to close them when finished. Never looked at routing or what they went to. Guess its about time I find out more about what lurks in the dark corners.

I do know now that only the first seacock is the raw water inlet and I now understand that the water circulates in the engine and exits via the exhaust.
 

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If the head is forward, the raw water seacock for it is also likely forward, not back in the engine compartment. :)
This was my thought. If the boat is equipped with a true marine head it's probably pulling raw water as well.
 

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Key word being "likely". I remember the raw water intake for my Dad's Chris Craft was back by the engine even though the head was quite a bit forward.

The only way to figure out what it's for is to follow it. Head or water maker are the only things I can think of that would use raw water. Most sinks and showers (at least that I have ever used) use fresh water.
 

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Plenty of boats have had salt water galley sink intakes, either hand or electric pumps, for rinsing dishes, or even for washing them, to conserve fresh water supplies for drinking/food preparation.
 

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Especially if the boat was outfitted for long distance cruising, since the water in most harbors is rather nasty... :)
Plenty of boats have had salt water galley sink intakes, either hand or electric pumps, for rinsing dishes, or even for washing them, to conserve fresh water supplies for drinking/food preparation.
 

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At the risk of being overly simple, I suggest that the second through-hull is to drain galley sink water. It is on my boat.
 

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Especially if the boat was outfitted for long distance cruising, since the water in most harbors is rather nasty... :)
Kinda like the water at RV parks. We always hooked up a 2 stage filter between the water supply and the hook up.
 

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Given that it was described as being beneath the engine... I'd guess it was below the water line. :)
Assuming it's above the waterline. The way it was described I think the seacock in question might be below.
 

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Assuming it's above the waterline. The way it was described I think the seacock in question might be below.
A below-water-line seacock will still drain a sink, as long as the bottom of the sink itself is above the waterline!;)
 

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on my hunter 27 the head intake is under the v berth starboard side, right next to the off shore holdng tank pump out. the sink has a large valve behind the galley cabinet under the cockpit. i have the hunter plumbing drawings and mine matches the drawing. i wonder if someone added a salt water rinse for the sink, how many faucets does your boat have? the only seacocks are the head flush and over board pump under the vberth, and the raw water intake under the engine per the drawing. the other must be added
 
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