25' Yanmar 3GM30 Exhaust Run (!)... Max Length / Height ?

[Sailmonkey]

It's just gas after the box, but is wet to the box. The exh from the engine will still mix with water, then exit the waterlift to an undisclosed location above the waterline where the magic of the box works. After that point it can go up/down/left/right so long as the drain line goes down and out (as short as possible and above the waterline so you can see the water). I should also mention that the drain line needs to be larger than your water supply to the engine, say 1 1/4" for a 3/4" supply.

The one I built was made of 1/8" doorskins for a basic shape, except for the bottom. I built it of epoxy and glass mat inside and out (more inside) then adden the three fiberglass pipes and base at the bottom, but used all mat and cloth for this part. Worked like a charm and I hope is still working to this day.

[sildene]

Originally Posted by akio.kanemoto

Howdy,

Also - something else that has been bothering me is that the exhaust run is all uphill until the gooseneck which will be just short of the outlet. I have a vetus waterlock which the specs say holds 5L.. exactly how much of the hose is filled with water? Definitely not 100%, but how little? The reason I ask is that when the engine is stopped, all the water in the hose will run back and fill the waterlock... looking at the exhaust run - I would have guessed that the hose would contain more than 5L and thus will fill the waterlock and fill the exhaust manifold etc... Thoughts?

I once had a fibreglass muffler made for a 16 foot wet line. Reading my old notes, the muffler fabricator was happy with my calculating the max liquid flow-back volume based on 25-30% of the line's air volume.

Martin

[akio.kanemoto]

Originally Posted by sildene

I once had a fibreglass muffler made for a 16 foot wet line. Reading my old notes, the muffler fabricator was happy with my calculating the max liquid flow-back volume based on 25-30% of the line's air volume.

Martin

Thanks muchly - that's perfect.

[never monday]

Originally Posted by akio.kanemoto

Also - something else that has been bothering me is that the exhaust run is all uphill until the gooseneck which will be just short of the outlet. I have a vetus waterlock which the specs say holds 5L.. exactly how much of the hose is filled with water? Definitely not 100%, but how little? The reason I ask is that when the engine is stopped, all the water in the hose will run back and fill the waterlock... looking at the exhaust run - I would have guessed that the hose would contain more than 5L and thus will fill the waterlock and fill the exhaust manifold etc... Thoughts?

Add the Vetus goodneck at the transom, or skip it and install a flap door on the outside. It's purpose is to keep following seas out.
The water travels up the hose in a layer against the side, not a slug between air pulses. A 5L water lock "might" be enough for that long of a run. If you could upsize it, it wouldn't hurt.

If your still having concerns about back pressure. Make the exhaust system out of 3" hose instead of the 2" normally on a GM series.

[cdennyb]

.445 psi is what the pressure is of a water column, take a pipe or hose or whatever and hold it up vertically. If it's 6' long and full of water then the pressure at the bottom is .44 x #of feet (6) = 2.67 in a perfect world. Just thought you'd like to know the pressure to overcome, it is a vertical component and does not take into consideration the loops, bends, restrictions, etc. of your tube run.