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Discussion Starter · #1 ·
I recently went from at 1/2" thru-hull to a 3/4" thru-hull for the raw engine water intake. So currently, all of the plumbing is 1/2", including the in/out for the raw water strainer. Is it recommended to change all of this plumbing to 3/4"? Or, is it just fine to reduce the tubing from 3/4" to 1/2" and keep the system as is?

I'm really wondering if I should get a 3/4" raw water strainer. I'd like to avoid this if 1/2" is acceptable.
 

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Hey 59r,

You didn't do anything except make the hole in your boat bigger. If your raw water cooling system works with 1/2", reduce the inlet and no worries. I have 3/4" everyhing to the pump, then 1/2" to the heat exchanger. I'd say you're good to stay the way you are (save on $ for all new hose, strainer, clamps etc.). :)

Dave
 

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Ok, I'll bite. Why did you drill a bigger hole in your boat? If it wasn't to fix a flow problem, I don't see why you can't just reduce it back to where it started.
 

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Discussion Starter · #4 · (Edited)
Ok, I'll bite. Why did you drill a bigger hole in your boat? If it wasn't to fix a flow problem, I don't see why you can't just reduce it back to where it started.
There was a gate valve in this location when I bought the boat, so I wanted to replace that. Through asking questions on SailNet, I found that 3/4" seacocks are the smallest size available based off of ABYC standards. My first project while the boat is in dry storage is to update the two 1/2" valve to 3/4" seacocks. I wanted the security of having the sturdy base along with the ball valve, plus meeting the ABYC standards.

The engine was being cooled very well with 1/2" plumbing. So again based off of the experience of the Sailnet sailors, I will reduce the 3/4" to 1/2" and keep the current plumbing unchanged. Thanks for the help; it is really appreciated.
 

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.......I found that 3/4" seacocks are the smallest size available based off of ABYC standards....
I'm not an ABYC expert, but I think you're saying that a 3/4" seacock is the smallest available in the quality specified by ABYC. It would seem strange to me that ABYC would require a larger hole than you actually seem to need.
 

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Discussion Starter · #6 ·
If I under stand you...you are correct...the wording I provided was confusing.

I found that seacocks aren't sold in 1/2". A 1/2" ball valve is available, but no base is sold in 1/2" (to make it a seacock). I was told in another thread that 3/4" seacocks were the smallest recommended by ABYC, so the suppliers only provide seacocks down to 3/4". I wanted seacocks for all of my thru-hulls, so I converted the two 1/2" valves to 3/4" seacocks.
 

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I would think that there is every reason to go up to 3/4 inch and not one for not doing so. Most yards will recommend 3/4" as a minimum; 1/2" is just too small. Any shell or partial obstruction of a 1/2" hole could spell disaster in some situations, whereas if 1/2" is required, a 3/4" thru hull makes a whole lot of sense, if partially blocked.
Put your reducer on the top of the thru hull after the valve, and you should be fine, though it would be better in the 1/2" began above the water line. You can always close the valve to clean out the 1/2" line if it becomes obstructed, which you cannot do with the thru hull without going in the water.
 

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It will cool the engine just fine, if unobstructed. The intake for my 3GMF on my Pearson 34 is 1/2" and gets eel grass and rock weed stuck before the strainer elbow once or twice a year. I have thought about changing to a larger strainer but, so far, have been too cheap to do it. I keep an eye on the temp gauge.
 

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3/4" will have 2.3 times the internal volume of 1/2" ... less pressure drop (resistance) = greater volumetric flow.
If you can easily afford it, go 3/4 all the way.
But, if mixing 1/2 and 3/4", keep all those 90° etc. elbows & 1/2 to 3/4 'reducers', etc. if needed to an absolute minimum.
 
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