KAD42 Exhaust

[jamescf]

Please can someone help with my knowledge of KAD42's . My exhaust elbows have a raw water inlet ex cooling system and also a second pipe flange steel pipe to hose on the side of the elbow that seems to lead down to the bottom of the exhaust pipe outlet. Is this second pipe for a balance or anti syphon or what ???
Thanks in advance.

 

[SimonD]

I'm told that it's a bypass in case the main exhaust blocks. Seems unlikely that would happen but it would be disastrous if it did. That said, the more I think about it, the less I think this is it's true purpose. I await an expert answer with interest!

 

[BruceK]

Back pressure. When the boat is not on the plane the depth to the exhaust on the cavitation plate gives too much back pressure so the exhaust vents out the transom shield

 

[jamescf]

Thanks Gentlemen. Looking at the Volvo schematic closely it would seem that the gasses could exit direct through the lump at the bottom of the exhaust pipe through the shield and thus provide an alternative outlet through the shield also less net positive head (back) pressure than through the out drive outlet that will be deeper in the drink. So both answers seem to fit to a degree.
Thanks again for your answers. At least now I know where the rubber hose goes to. What a great font of knowledge this forum is with many able to provide answers and advice. Thank you all for taking the time to answer me. A newbie on KAD42's.