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Saildrive Raw Water Flow Causing Flooded Engine.


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49 minutes ago, dutyfree said:

But if the issue is on the intake side how does an exhaust riser fix it?

A picture is in order.... So long as the exhaust riser is above the exhaust system at all heel/pitch angles the raw water cannot get back into the exhaust outlet.

Some boats have a valve on the exhaust. Closing that could cause the water to come back up the exhaust riser. 

Screenshot_20201217-223327_Bamboo Paper.jpg

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On 17/12/2020 at 10:33 PM, CarpeDiem said:

A picture is in order.... So long as the exhaust riser is above the exhaust system at all heel/pitch angles the raw water cannot get back into the exhaust outlet.

Some boats have a valve on the exhaust. Closing that could cause the water to come back up the exhaust riser. 

Screenshot_20201217-223327_Bamboo Paper.jpg

Yep, I can see how that would work

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On 17/12/2020 at 6:27 PM, CarpeDiem said:

Gravity stops the water going up the riser.  The water is pushed out the exhaust pipe. Because the exhaust riser is above the exhaust and inlet system. 

Essentially then if there is any risk of the raw water system  being submerged  have an anti siphon loop (ASL)  between the pump and the heat exchanger as well as an exhaust riser.

The ASL prevents a siphon effect creating undesirable raw water flow when sufficiently heeled. The Exhaust riser prevents the engine being flooded should water fill the exhaust from either issue ie

(a) A siphon effect as mentioned above or,

(b) Elevated pressure from  very high sailing speeds forcing water circulation, which is presumably only a worry for fast multihulls.

 

 

 

 

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