[Peter Bierman]

Hello everybody,

Finished installing my replacement engine. I used the outlet system which was installed originally.

This is the one with the big brass silencer with the bulky brass tube, going from exhaustmanifold underneath the silencer.

How Ifound out that water was flowing back to the cylinderhead? One of the sealings was leaking some wet dirty water!!! I took away the exhaustmanifold to solve the problem and found the water pouring out of the cylinderhead openings. Starting the engine gave a good dirty shower and cleaned it out.

Possibly this problem ruined my old engine, once had a waterlock while starting!!!

In my opinion the silencer is defective or the original design was not to good. Maybe special, engine stop, procedure required? 

I looked into the silencer through the short pipe which goes to the rubber tube, but could not see much. I noticed a piece that looked ripped off at the beginning of this tube.

Questions: Is anyone familiar with this silencer? Are there drawings of this silencer available?

Any suggestions to solve this problem are very welcome.

Peter Bierman, A31/9

 

 

Topic

[Trevor Thompson]

Peter

I will look up the catalogue to see if the association has drawings for this exhaust – but I dont remember seeing such a drawing.

 

While I cannot claim expertese regarding this specific engine installation, or even to have seen an engine installation in an A31, I can claim experience of similar systems.

 

It sounds like your exhaust manifold is too close to the waterline, or perhaps even lower than the waterline. A fairly standard problem with standard solutions. In modern installations this requires a syphon breaker in the water inlet line between the sea cock and the water pump. It also requires a “swan neck” in the exhaust to raise the pipe up to deck level before it falls back down to the exhaust outlet so that water cannot flow back down the exhaust. This modern practice would use a rubber exhaust pipe and inject the water into the exhaust just where the exhaust becomes rubber. A low section in the rubber pipe is used to allow the water left in the exhaust to settle into. The two elements go together. The swan neck stops the water flowing in from the exhaust, and the syphon breaker prevents water from flowing in through the water pump from the cooling water inlet.

 

Now to your installation. Since you are getting water into the engine I suspect that your engine is low enough to need the precautions mentioned above.

You have not mentioned whether you have a syphon breaker in the inlet line. You do need it.

If I describe the exhaust fitted to the A26 when new you can let me know if yours fits this description. The exhaust from the engine to the transom consisted of two pipes one inside another. The water ran between the two pipes so thet the inner pipe was a dry exhaust, surrounded by a water jacket. Near the transom there was a box where the water was mixed with the exhaust just before it went overboard. This box acted as a swan neck.

 

If that sounds like your exhaust then it probably has corroded through internally and is allowing water back into the engine. It will not be repairable if it is this old, and having a replacement made as a copy will be expensive. The solution will be a modern rubber system with plastic silencer, swanneck and skin fitting. I suspect you will have to make an injection bend as well.

 

I think that you need to replace the whole exhaust anyway if what you have is the original. You should not take chances with exhausts because of the risk of poisonous fumes entering the accomodation, and the risk of engine failure.

 

Hope this helps

 

Trevor

 

 

[Peter Bierman]

Hi Trevor,

Just finished cutting the silencer as I figured that it is defective anyway. Than I read your message. The description from you about the A26 silencer is about what I found. The silencer is burned through inside.

Making a new exhaust system is the only way now. It should not to be difficult because the old silencer was fitted about 80cm above waterline. (measures of the A31 are rather big).

For interest I added a few photographs of the cut open silencer.

Thank you for the advice it helps a lot to choose the proper parts. 

Kind regards, Peter.

[Trevor Thompson]

Peter

 

Not surprised to hear its burnt through. It has done pretty well to have lasted this long.

 

I would put oil into the bores and valves to make sure they dont rust up over the next few months.

 

Best wishes

 

Trevor

[David Gray]

Trevor Thompson said:

Peter

I will look up the catalogue to see if the association has drawings for this exhaust – but I dont remember seeing such a drawing.

 

While I cannot claim expertese regarding this specific engine installation, or even to have seen an engine installation in an A31, I can claim experience of similar systems.

 

It sounds like your exhaust manifold is too close to the waterline, or perhaps even lower than the waterline. A fairly standard problem with standard solutions. In modern installations this requires a syphon breaker in the water inlet line between the sea cock and the water pump. It also requires a “swan neck” in the exhaust to raise the pipe up to deck level before it falls back down to the exhaust outlet so that water cannot flow back down the exhaust. This modern practice would use a rubber exhaust pipe and inject the water into the exhaust just where the exhaust becomes rubber. A low section in the rubber pipe is used to allow the water left in the exhaust to settle into. The two elements go together. The swan neck stops the water flowing in from the exhaust, and the syphon breaker prevents water from flowing in through the water pump from the cooling water inlet.

 

Now to your installation. Since you are getting water into the engine I suspect that your engine is low enough to need the precautions mentioned above.

You have not mentioned whether you have a syphon breaker in the inlet line. You do need it.

If I describe the exhaust fitted to the A26 when new you can let me know if yours fits this description. The exhaust from the engine to the transom consisted of two pipes one inside another. The water ran between the two pipes so thet the inner pipe was a dry exhaust, surrounded by a water jacket. Near the transom there was a box where the water was mixed with the exhaust just before it went overboard. This box acted as a swan neck.

 

If that sounds like your exhaust then it probably has corroded through internally and is allowing water back into the engine. It will not be repairable if it is this old, and having a replacement made as a copy will be expensive. The solution will be a modern rubber system with plastic silencer, swanneck and skin fitting. I suspect you will have to make an injection bend as well.

 

I think that you need to replace the whole exhaust anyway if what you have is the original. You should not take chances with exhausts because of the risk of poisonous fumes entering the accomodation, and the risk of engine failure.

 

Hope this helps

 

Trevor

 

 

[David Gray]

     Thanks Trevor for your clear exhaust exposition. I have used twin injection s/s pipes into the s/s exhaust pipes on my refurbished CV WN4, but they are probably too close to the manifolds at the moment, so I will move them out further and lower, to inject just before a new s/s Y junction attaches to the rubber exhaust.

      New keel bolts and jack u-pieces will be installed as soon as the snow clears.          David Gray A49  

[Author]

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