Elbow exhaust carbon build up

[geekoman]

My Yanmar 4JH57 engines are at 500 hours, I purchased the boat used. I wanted to check the exhaust elbows for the first time which is a simple matter on the engine side, a bit more challenging on the exhaust hose side.

Nonetheless, can I get a quick critique on this photo on the engine side? Really clean? As expected? Try to run hotter as they should be silver inside?

I'll tear into the exhaust side and see how the saltwater has impacted the piping over time when I get a chance to ensure I can get the hose back on and have a usable engine when needed.

Thanks!

[skipperpete]

Yanmar publishes a service life for that mixer elbow at 500 hours and for a very good reason. The weld between the mounting flange and the inner pipe in your photo is also the sealing edge for the raw water at the injection point and it eventually cracks and corrodes through to the raw water side. Yours is already showing signs of corrosion and what appear to be droplets of water on the black soot. Eventually the corrosion attacks the alloy heat exchanger mounting face, sometimes requiring a new heat exchanger housing at the worst or a difficult welding repair at best. Take a close look at the area that the mixer elbow attaches to for a better idea of what’s happening re corrosion. The geometry of the injection point seems perfectly placed to allow raw water to briefly trickle into a cracked/corroded weld at engine shutdown , more so on a saildrive installation with the engine horizontal rather than inclined. ..... no problem while the engine is running though.
Finally, the cracked weld can be re welded ...... and the soot in the elbow appears about normal apart from those suspicious droplets.
Pete.

[barnakiel]

Looks clean.


Wash, slean, pain as required then use a new gasket, etc. Fit. Next stop in some 500 hours.


b.

[Compass790]

If it was me I'd replace with an ss elbow if the Yammer one has only a 500 hr life.
Try exhaustelbow.com or there are others.
Be cheaper & better than yanmars.