Designing a new exhaust riser and waterlock for the MD2B

[Akestor]

Hello!
This topic must have been discussed countless times ( since nobody wants a hydrolock!).

At the upper sketch is the exhaust system currently, which i dont like and it is time to go for a new system. The reason is that both the single jacket elbow and the waterlock (both made from SS) are leaking. The elbow is not rising at all- also the waterlock is very tiny, no more than 2 litres, and the hose very long, around 3.5 meters ( 45 mm hose should keep around 5,5 litres)..There are 2 goosenecks one immediatly after the waterlock and one at the stern..

The second sketch is what i would like to build. A dry riser from 1 1/4 plumping accesories and a 6 litre epoxy waterlock . In the new design i will cut around 50 cm of the hose and remove the first gooseneck as i find it unnecessary with a 6 litre waterlock. The length of the hose will be 3 meters which will keep around 4,7 litres.
I think this design should be ok. your thoughts!?

 

[LittleSister]

I don't know the diameter of your hose, so can't check your volume calculations, but note that the waterlock only needs to contain a % of the hose volume, as the hose is never full of water (an engine ejects mainly gas). A relevant calculation/safety factor is given in the excellent diagrams and guidance in the Vetus catalogue. (IIRC, and I'm not sure I do, it assumes a max of 50% of exhaust hose volume will be water.)

Depending on the level of your engine compared to the waterline, a gooseneck at the engine may well not be required. (The watercock should adequately contain all the water form the engine and exhaust hose. Again see Vetus guidance.

Link to Vetus catalogue (see page 84): http://viewer.zmags.com/publication/4a7db1e9#/4a7db1e9/1

 

[BabaYaga]

I think this design should be ok. your thoughts!?
]

I think there should be an anti-syphon device in the cooling water pipe.

 

[coopec]

I strongly recommend you read this article on marine engine exhaust design as the author is highly critical of some of the designs proposed by "experts".

https://www.sbmar.com/articles/designing-a-marine-exhaust-system/

Of course BabaYaga is correct in saying there should be an ant-siphon loop.

 

[Akestor]

I strongly recommend you read this article on marine engine exhaust design as the author is highly critical of some of the designs proposed by "experts".

https://www.sbmar.com/articles/designing-a-marine-exhaust-system/

Of course BabaYaga is correct in saying there should be an ant-siphon loop.

I have read this article very informative thanks!

 

[Akestor]

I don't know the diameter of your hose, so can't check your volume calculations, but note that the waterlock only needs to contain a % of the hose volume, as the hose is never full of water (an engine ejects mainly gas). A relevant calculation/safety factor is given in the excellent diagrams and guidance in the Vetus catalogue. (IIRC, and I'm not sure I do, it assumes a max of 50% of exhaust hose volume will be water.)

Depending on the level of your engine compared to the waterline, a gooseneck at the engine may well not be required. (The watercock should adequately contain all the water form the engine and exhaust hose. Again see Vetus guidance.

Link to Vetus catalogue (see page 84): http://viewer.zmags.com/publication/4a7db1e9#/4a7db1e9/1

Its a 45mm hose, and the litres mentioned are in the case that the whole length if full of water. Thanks for the link!

 

[Akestor]

I think there should be an anti-syphon device in the cooling water pipe.

Yes i will install an antisiphon valve in the new installation.