Do all boats have seacocks for the raw water cooling system?

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Han_solo

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Mines a Sealine 305 Statesman and I can't seem to see any, looked all over the engine(s) compartment and nothing. Am I looking in the wrong place or is it that some older boats, ( mine is an 1985 ), didn't have them ?


Perplexed.
 
No
Outdrives water enters from a vent fwd facing at the foot of the leg .Its then plumbed to the strainer then raw water pump and dumped via the riser through the lower belows into the leg exhaust .You see nothing externally.

Inboard ( none outdrives) will have a separate seacocks to a strainer then to the R water pump .
Once circulated through the various heat exchangers it’s then dumped into the exhaust ( to cool ) and some as well maybe sent overboard separately into a fart pipe which is a visible tell tale waters circulation is occurring.
 
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Isn't that boat outdrive powered? If yes, raw water for engine cooling is picked through the legs.
 
jrudge said:
It does always amaze me that there are no sea cocks on an out drive boat !
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I can tell you why, it’s because the impeller is outside the boat and in stern drive itself under the waterline , water can not pass the impeller unless it is rotating , hence the impeller is essentially an automatic seacock. In an inboard engine, there is a length of tubing and usually a strainer before you get to the impeller, any leakage in this pre-impeller system will fill your hull with water and hence the need for a seacock.
 
benchmark said:
I can tell you why, it’s because the impeller is outside the boat and in stern drive itself under the waterline , water can not pass the impeller unless it is rotating , hence the impeller is essentially an automatic seacock. In an inboard engine, there is a length of tubing and usually a strainer before you get to the impeller, any leakage in this pre-impeller system will fill your hull with water and hence the need for a seacock.
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That's true for some outdrives, merc alpha one for example,but definitely not true for all, for example Volvo penta dph outdrive which have the impeller/pump mounted on the engine. The design of the dph raw water feed tries to limit the possibility of flooding the boat by having a kind of reverse u bend hose (and n bend??) immediately after the outdrive,which lifts the height of the hose above the waterline as soon as is practically possible, but not sure how effective this would be in practice, but like Pete says you don't hear of many outdrive boats sinking this way.
 
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petem said:
But how many do you know that have sunk from the lack of them?
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They were initially designed for little day boat runabouts which spent downtime on a trailer,drystack or in shed during a Swedish winter .

How ever now they appear on 45 ftr s eg Abolute etc which spend generally if in the Med 51 weeks in the sea .
So I would seem to me Jez has a point .
Just packed up for the season yesterday and turned ALL the seacocks off .Suitably labelled and marked .
Will revisit periodically and run systems up over the winter .

So it makes sense in a risk assessment kinda way to able to isolate a sterndrive seawater supply , both in and out *,if it’s ( as is the way theses days ) left in the drink over the winter .

* Outs tricky as unlike conventional shaftdrive stern drive exhaust dissapears at the back close to the transom with the “ riser “ to the lower belows .
 
julians said:
That's true for some outdrives, merc alpha one for example,but definitely not true for all, for example Volvo penta dph outdrive which have the impeller/pump mounted on the engine. The design of the dph raw water feed tries to limit the possibility of flooding the boat by having a kind of reverse u bend hose immediately after the outdrive,which lifts the height of the hose above the waterline as soon as is practically possible, but not sure how effective this would be in practice, but like Pete says you don't hear of many outdrive boats sinking this way.
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I did not know Volvo was designed this way but the hose above the waterline does seem to be a smart idea . I have only owned Mercruiser alpha drive and I never worried about water ingress via the cooling circuit as much as I worried about water ingress in case of a failed bellow .
 
benchmark said:
I can tell you why, it’s because the impeller is outside the boat and in stern drive itself under the waterline , water can not pass the impeller unless it is rotating , hence the impeller is essentially an automatic seacock. In an inboard engine, there is a length of tubing and usually a strainer before you get to the impeller, any leakage in this pre-impeller system will fill your hull with water and hence the need for a seacock.
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My boat is stern drive but the raw water pump containing the impellor is on the front of the engine.
 
The water pump on the D4 is above the waterline; the suction hose leading to it is not for some of its length. Hoses on the suction side don't normally spontaneously fail.
 
GrahamHR said:
The water pump on the D4 is above the waterline; the suction hose leading to it is not for some of its length. Hoses on the suction side don't normally spontaneously fail.
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Agreed, but on this basis they might not fit seacocks in shaft boats as well... :ambivalence:
 
My boat has a mercury TDI (VW) and s Bravo 3 drive and it has a seperate raw water intake and seacock. What dies that mean fir the impeller in the drive unit or will thst be removed?
 
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