Exhausting questions

[michael_w]

Is there a rule of thumb for sizing waterlocks?

I'm in the process of repowering, though the new engine has the same exhaust diameter as the old one, I know it pumps a lot more water. I'm concered that the existing waterlock which looks a bit puny might not be able to cope.

The Vetus catalogue is silent on this subject.

 

[richardabeattie]

What is the engine? How big is the existing waterlock?

 

[michael_w]

Old engine Volvo 2003, new engine Volvo 2003T. The turbo has a high capacity raw water pump compared to the natural aspirated version.

 

[boatmike]

The size of the engine and throughput of water is immaterial if the pipe diameter is the same. There must be sufficient capacity in the waterlock to ensure that any water in the system when you switch off does not return to the engine. The usual rule of thumb is to make the waterlock run back capacity greater than the volume in the rising pipe to the manifold.

 

[michael_w]

Thanks, I think I'll include the capacity of the exhaust tube from the waterlock to the gooseneck too. Gawd knows why the engine hasn't filled up with water some time in the past 20 years.

 

[SlowlyButSurely]

I have found on my boat that the height of the exhaust outlet above the waterlock has a significant effect on the amount of water that remains in the waterlock while the engine is running, so this volume needs to be added into the total as well. Also, there is more water in the waterlock when the engine is ticking over than when running at full throttle. Don't know how you would find this out except by experimentation.