engine sea cock -- open or closed

[Skipperobb]

Hi All

Can anyone clarify the seacock open vs closed arguement.   Recently had the BUKH10 overhauled on my C29, the mechanic advised me to leave the seacock on the engine open permantely as this is better for the engine after shut down.     Apart from the obvious -- if it leaks the boat will sink-- is there any real benefit in leaving the seacock open?  Is it to do with pressure in the cooling system as the motor cools or is it to keep the water pump dry ( i assume if left open the water will drain out of the cooling system.   Any ideas ??  Noel

[HarbourHack]

Not sure about the cooling thing, but I trust stainless steel over rubber to protect my boat from sinking any day!

[Maeling]

Never heard of that one - except to remember to turn it on next time you start! Logically the water in the jacket must boil off a bit but can't see any issue there. One thing I am going to play with is a Y cock on the inlet, so I can run a bucket of fresh water into the system before shutdown. (I have an alloy block).
Geoff Raebel

[Jon Douglas Haynes]

I have never  thought of closing the sea cock whilst underway  . stating the obvious it stays closed whilst the boat is alongside or at the mooring .
Im not sure about about shutting down a hot engine with only the water in the engine jacket >
 

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Date: Mon, 16 Jul 2012 00:51:22 -0700
From: skipp...@optusnet.com.au
To: compass-y...@googlegroups.com
Subject: engine sea cock -- open or closed

Hi All

Can anyone clarify the seacock open vs closed arguement.   Recently had the BUKH10 overhauled on my C29, the mechanic advised me to leave the seacock on the engine open permantely as this is better for the engine after shut down.     Apart from the obvious -- if it leaks the boat will sink-- is there any real benefit in leaving the seacock open?  Is it to do with pressure in the cooling system as the motor cools or is it to keep the water pump dry ( i assume if left open the water will drain out of the cooling system.   Any ideas ??  Noel

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[Djarraluda]

No justification to leave seacocks open when unattended.  It is a risk and should not be contemplated.

If there ever was some issue re engine cooling, then expansion still happens at the outlet, so why????

I would not be suprised to hear insurance companies objecting to the practice of leaving open seacocks below the waterline and there is no serious sailor who would ever contemplate such

If someone is even likely to leave seacocks closed, as we have with some sail training, or charter boats, then we have a small sign "open seacocks before starting" and hang it on the throttle or other visible location.  One boat I used to sail had the engine key on the notice and hung it on the seacock - it worked, nobody ever started the engine withpout opening the seacock.

On Monday, July 16, 2012 5:51:22 PM UTC+10, Skipperobb wrote:

[Les Fairwind]

Hi

 

I always close my kingston cock when I turn the engine off, straight away.  I was advised to do this by an old sailer, his idea was that if you close the inlet, you keep the water in the engine cooling system.  If you let it drain out an open seacock, the falling salt water evaporates and leaves a salt rime to build up over time in the cooling chambers bizzos.  Mine is raw water cooled, but I assume the same theory applies to heat exchangers.

 

Also, with the seacock open, if I heel over too much while sailing I can get a gutful of air in the kingston cock, that causes an air lock in the water pump and cooling system, stopping the water pump from pumping water, causing the water lock to burn out, filling the boat with diesel smoke  . . .  I am lucky with my motor though, if it overheats it seizes up, but after sitting for about 15 minutes it cools and shrinks back to size and away we go again.

 

I also put a Y-valve to flush with fresh water, but if anyone is thinking of doing the same, don't use a T-valve, there is not enough suction on the water pump, a Yvalve is best.  Another good use is if you get an air lock as above, you can prime the other tube on the Y-valve to remove the airlock.