Any ideas why somebody would make an exhaust riser like this? It appears that the flange that bolts to the Head only has two bolts I believe it should have four. The exhaust elbow at the top is a westerbeak.
Volvo Penta 2003, exhaust.
- Thread starter Whitby-42
- Start date
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 22,363
The design is to get the exhaust above the waterline then inject water so that it runs downward to the exhaust exit which looks to be below the boats waterline. Many ways are used to solve the exhaust problem. If it is working I would not mess with it.
Regarding the exhaust manifold flange, how many studs or bolts are on the exhaust manifold. My Perkins has 4. The engine builder made that decision. If only two I would expect the studs to be large. I would monitor the flange to assure no cracks in the metal.
Regarding the exhaust manifold flange, how many studs or bolts are on the exhaust manifold. My Perkins has 4. The engine builder made that decision. If only two I would expect the studs to be large. I would monitor the flange to assure no cracks in the metal.
The exhaust exits through stern of the boat about 2 ft above the water line. So if I'm understanding you correctly the mixing elbow should be slightly above the height of the exhaust port out the back?
Do you know if there's a proper height placement of the muffler?
From every photo I have seen of the Volvo Penta 2000 series they all have four bolts. The owner prior to the previous owner had stated the original mixing elbow was completely rotted. I would assume that two of the four bolts were stripped/ rotted out.
When the engine is running the thing is vibrating back and forth I don't feel that it is going to last at all with that mixing elbow up so high and weighing probably 15 pounds. If it's necessary that it be so high it at least needs a brace to the top of the riser or to the mixing elbow.
This image pretty much explains everything I need to know except one thing I'm confused on is in the article it says engines near or below water line should have an anti-siphon valve though in the bottom depiction of the image there is no anti-siphon valve?
The raw water in the bottom diagram drains into the muffler only and that is the siphon break. Once the engine stops running, only exhaust gases are in the piping to the muffler. The raw water can not climb up to the engine exhaust. Looks strange but it works correctly.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 22,363
My education on my boat about exhaust developed these specifics.
Here is my exhaust pipe and water insertion setup.
- You need to inject the water into the exhaust so it will not backflow into the manifold.
- When the engine is below the waterline, the exhaust must rise above the waterline before water is injected.
- To prevent burns, you must wrap the exhaust pipe from the exhaust manifold to the water insertion point.
- Without a water muffler, to prevent water backflowing up from the exhaust pipe, you must have a rise in the exhaust hose above the water line a minimum of 12 inches and direct the exhaust in a downward flow to the outside of the hull.
Here is my exhaust pipe and water insertion setup.