dutyfree 81 Posted December 17, 2020 Report Share Posted December 17, 2020 But if the issue is on the intake side how does an exhaust riser fix it? Quote Link to post Share on other sites
CarpeDiem 21 Posted December 17, 2020 Report Share Posted December 17, 2020 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. Quote Link to post Share on other sites
Bad Kitty 117 Posted December 17, 2020 Report Share Posted December 17, 2020 Don't think so, but I've got a pretty short attention span, so that's me. I'm happy that what we've got works, & that wouldn't for us. Happy Xmas Quote Link to post Share on other sites
Frank 23 Posted December 19, 2020 Author Report Share Posted December 19, 2020 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. Yep, I can see how that would work Quote Link to post Share on other sites
Frank 23 Posted December 19, 2020 Author Report Share Posted December 19, 2020 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. CarpeDiem 1 Quote Link to post Share on other sites
waikiore 62 Posted December 24, 2020 Report Share Posted December 24, 2020 CD I have seen your diagram type system fail but it was a hi speed multi hull 30 plus and the drawing is more typical of a launch installation (American) than a typical yacht, where the waterlock and subsequent rise till dropping to skin fitting aft creates a bit of back pressure. Quote Link to post Share on other sites
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