Seacock size

[azazzera]

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.

[Ajax]

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.

Be 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.

[67c&ccorv]

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.

Big enough to allow small marine animals and other assorted debris into the cooling system?



3/4" is plenty big enough.

[BunnyPlanet169]

3/4" is enough. Note the all the fittings starting at the inlet of the pump and onward are smaller....

[lat 64]

Be 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.

+1 on all that Ajax said.
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.

[Ajax]

+1 on the cockpit drains.

[Mark Millbauer]

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"

[BunnyPlanet169]

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"...

[lat 64]

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"

Mine 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

[67c&ccorv]

Mine 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

That's what happened with me too Russ - good quality 3/4" seacocks came up at a steal...that's my engine "automatic" water intake taking shape in the bilge.

[romantic comedy]

Inch and a half is enough for mermaids to get in.

[hanleyclifford]

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.

[toddster]

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.

[Mark Millbauer]

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.

Mark

[ndutton]

Mark, I replaced my 1/2" RW thru-hull with an open 3/4" for a number of reasons:

1. 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.
2. 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.
3. 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.