Exhaust system

[Pladdatoo]

Hi All

Having followed the various threads about Yanmar exhaust mixing elbows rusting out, I decided to go and fully investigate the exhaust system on my boat as it is an area I know very little about and thought it was something I should brush up on.

The engine in question is a Yanmar 3GM30 Raw water cooled - I have attached a photo which shows it from the rear.
It appears to have a Vetus Waterlock LP (out of shot in the photo) which is installed low down in the engine bay, and an anti-syphon device which is visible in the photo (blue pipework).

Of particular note is that the elbow is not cooled directly (so it appears to me), so I was wondering whether rusting out is something I need concern myself with?


Of particular interest to me is what maintenance should I be concerned with doing on this sort of set up. ? Are there particular issues that others have found that I should bear in mind?
I assume that the use of a waterlock is standard and is used to quieten the engine and prevent back-flow into the engine from the waste. Is that correct?

Your thoughts as usual are appreciated.

Pladda

 

[Tranona]

Suspect there is a channel inside the exhaust manifold to both cool the exhaust and then inject the water into the elbow, so there will be a point where the water mixes with the gases before it goes down the rubber hose. I expect the Yanmar workshop manual will show how this works.

You are correct in your description of the function of the water trap and the placing of the anti syphon valve. Not fully clear whether the valve is a valve or an open bleed, probably the former, in which case worth dismantling and cleaning. No routine maintenance needed on the Vetus trap other than draining it if you lay the boat up in a really cold place where heavy frosts are likely.

 

[Pladdatoo]

Thank you Tranona. I will check the manual next time on the boat.

I decided to pull the three anodes yesterday and was pleased to see that they were being gently eroded, so at least they are going rather than bits of the engine !

Noticed a fair amount of deposit in the holes the anodes came out of, so trying to work out a way of cleaning out the waterways. I assume that there is a thermostat some where in the system, so will want to get that opening up so as to be able to get at all the various channels . I was planning on using central heating cleaner and getting that nice and hot.

 

[RichardS]

Thank you Tranona. I will check the manual next time on the boat.

I decided to pull the three anodes yesterday and was pleased to see that they were being gently eroded, so at least they are going rather than bits of the engine !

Noticed a fair amount of deposit in the holes the anodes came out of, so trying to work out a way of cleaning out the waterways. I assume that there is a thermostat some where in the system, so will want to get that opening up so as to be able to get at all the various channels . I was planning on using central heating cleaner and getting that nice and hot.

As Tranona says, if there is water spraying out of the exhaust when the engine is running it must be being injected somewhere before the rubber exhaust hose. The ridge at the top of the elbow is probably the cast-in waterway that Tranona refers to.

Richard

 

[NormanS]

There seems to be a lot of loose wires hanging around!

 

[Pladdatoo]

There seems to be a lot of loose wires hanging around!

Yes. I hang fairy lights off them at Christmas time