I have now a 3/4 inch raw water seacocks for the a4. I have removed and will glass over a 1.5 seacock that was a head discharge. Planning on composting toilet in future. My question is whould it benefit the engine at all to have a 1.5 inch inlet over the 3/4. I know that 1.5 is over kill but is 3/4 adiquite. Wat are the thoughts. I would rather not have to enlarge the hole but will if 3/4 is not enough water flow for the pump. Thanks. Btw both seacocks are WC cone type.
Seacock size
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Originally posted by azazzera View PostI have now a 3/4 inch raw water seacocks for the a4. I have removed and will glass over a 1.5 seacock that was a head discharge. Planning on composting toilet in future. My question is whould it benefit the engine at all to have a 1.5 inch inlet over the 3/4. I know that 1.5 is over kill but is 3/4 adiquite. Wat are the thoughts. I would rather not have to enlarge the hole but will if 3/4 is not enough water flow for the pump. Thanks. Btw both seacocks are WC cone type.
My boat originally came with a 1/2" through hull. I upgraded to a 3/4" and removed the 90 degree elbow on the original seacock. This greatly improved flow.
A future owner of my boat, might look at my 3/4" through hull and think "Hm, maybe I should make this bigger!" Before long, you've got a 1-inch through hull for an engine that really doesn't need it.
I've heard of similar "upgrade spirals" happening for standing rigging as well.
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Originally posted by azazzera View PostI have now a 3/4 inch raw water seacocks for the a4. I have removed and will glass over a 1.5 seacock that was a head discharge. Planning on composting toilet in future. My question is whould it benefit the engine at all to have a 1.5 inch inlet over the 3/4. I know that 1.5 is over kill but is 3/4 adiquite. Wat are the thoughts. I would rather not have to enlarge the hole but will if 3/4 is not enough water flow for the pump. Thanks. Btw both seacocks are WC cone type.
3/4" is plenty big enough.
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Originally posted by Ajax View PostBe careful not to get "upgrade fever".
My boat originally came with a 1/2" through hull. I upgraded to a 3/4" and removed the 90 degree elbow on the original seacock. This greatly improved flow.
A future owner of my boat, might look at my 3/4" through hull and think "Hm, maybe I should make this bigger!" Before long, you've got a 1-inch through hull for an engine that really doesn't need it.
I've heard of similar "upgrade spirals" happening for standing rigging as well.
I have a 1/2-inch on my engine intake and it's working fine now, but I got a great deal on 3/4-inch seacocks and will go with that.
I am just today going to finish the backing plates and prep work for this job. I will post some pics on an old thread I started last fall. I had some poor setups on most of mine.
My cockpit drain is going from 3/4-inch to 1.5 inches. That's a place where bigger is better.sigpic Whiskeyjack a '68 Columbia 36 rebuilt A-4 with 2:1
"Since when is napping doing nothing?"
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Engine Thru-hull size.
I have my 78 C30 on the hard for bottom paint and a few other maintenance items. I notice that my engine raw water intake is 1/2". The boat originally had a raw water cooled Yanmar 12 HP diesel in it. It now has a fresh water cooled A4. Does anyone know if the A4 requires a 3/4' intake thru-hull?
Mark
C30 "Kismet"Mark
C30 "Kismet"
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The usual raw water pump is plumbed for 3/8" NPT. That is the limiting size.
Anything larger than that is fine, and 1/2" and 3/4" are pretty standard, leaning towards the 3/4"...Last edited by BunnyPlanet169; 03-23-2015, 01:53 PM.Jeff
sigpic
S/V Bunny Planet
1971 Bristol 29 #169
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Originally posted by Mark Millbauer View PostI have my 78 C30 on the hard for bottom paint and a few other maintenance items. I notice that my engine raw water intake is 1/2". The boat originally had a raw water cooled Yanmar 12 HP diesel in it. It now has a fresh water cooled A4. Does anyone know if the A4 requires a 3/4' intake thru-hull?
Mark
C30 "Kismet"
Russigpic Whiskeyjack a '68 Columbia 36 rebuilt A-4 with 2:1
"Since when is napping doing nothing?"
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Originally posted by lat 64 View PostMine was 1/2" for 43 years. Works fine. Like I said, I'm just going to 3/4" cause I bought three at a good price. The intake screen was almost filled up with bottom paint too, and it still flowed enough. Just keep it clean and I think you're good.
Rus
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Fwiw
The answer to the question depends a lot on how you use your boat. I used to have a 3/4" raw water intake and it worked fine in normal conditions, but in heavy seas I found myself losing prime on the pickup side and I attributed it to hull configuration and minimum capacity in the pickup side. When I went to the 1" thru hull the problem disappeared in even the nastiest conditions.
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The only advantage that I can think of for using the 1.5" as an intake, would be to set it up as a "sea trunk" manifold serving all of your raw-water needs from one valve. Engine, head, wash-down pump... maybe a raw-water pre-wash tap for the galley sink? Personally, I don't think I'd go there.
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Thanks for the input. I think I'll stay with the current 1/2" set up for now since it seems to be adequate thus far and the valve seems to be in good shape. As I have in the past with previous boats, I'll upgrade to 3/4 should my valve or thru-hull need some attention.
MarkMark
C30 "Kismet"
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Mark, I replaced my 1/2" RW thru-hull with an open 3/4" for a number of reasons:- The external grate on the original made it impossible to clear an obstruction from inside the boat by removing the hose, opening the valve and giving it the ole' roto-rooter.
- The grate and small I.D. of the 1/2" thru-hull made it impossible to get bottom paint up inside there to prevent occluding growth.
- I wanted the smallest restriction and therefore the catch point to be a serviceable raw water strainer (Groco ARG-750 in my case) easily accessible in the engine space. Being in SoCal near a major metropolis and commercial harbor we have all sorts of debris and kelp that can obstruct the raw water intake so being able to clear it easily is important.
Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
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