Exhaust elbow placement and concerns....

[teneicm]

We have a Kubota engine who's exhaust elbow has cracked and requires replacement. The elbow that's currently on the engine comes off the manifold and rises about 18 inches before it bends downward slightly and attaches to the exhaust hose and muffler.

The replacement elbow being sold by Phasor Marine (the company that marinizes Kubotas) is only about 5 inches long. They say the elbow on my engine is some aftermarket part they're not familiar with.

Is there any reason that I couldn't use the smaller elbow? Is there any requirement of the height of the elbow with respect to the waterline that I should be concerned about? It's a new to us boat, so I have no idea why such a large elbow was used in the first place....


Thanks! Matt

[Mimsy]

We could not find an exhaust elbow for our Perkins and had to have one made by a machine shop. When it comes to engine parts, I just think it is always a good idea to keep things as they are unless absolutely necessary to change.

Where is the closest machine shop to you? Shipping the old elbow out, manufacturing a new one and having it shipped might be a PITA unless you have an open calendar.

[model 10]

Before you change the design you should understand water lift exhaust systems.

[JK n Smitty]

There are some concerns relative to the height of the waterline and the manifold. Also, what other equipment you have plays into it. For instance, do you have a waterlift muffler installed?

Here is th ABYC standards for exhaust. There are some pictures and explainations that should help you.

Also, if you click on my blog (in the signature) I built my own from parts at the home store and posted some step-by-step details on how I did it. The one thing I would do different is use galvanized steel. When I built it I was concerned about metal fume fever but since making mine I did some additional research and found out the temperature needs to be much hotter than what we generate on boats.

Good luck and fair winds,

Jesse

[teneicm]

Jesse- Thanks for that link to the ABYC. Yes, we also have a waterlift muffler at the lowest point. Our system is basically described in Fig. 5, but in our case the elbow/riser also goes above the waterline. We have a siphon break loop on the cooling water line that goes above the waterline as well. Having both the elbow/riser AND the siphon break be above waterline seems to doubly reduce the risk of water back flowing into the engine, but doesn't seem to be required.

I'd happily keep the design the same, but I have no idea where to source the part that's on there now. Anyone know where I could look? Exhaustrisers.com doesn't seem to exist yet! Or, if anyone knows a good custom shop in the Abacos or SE US, we could also try the custom fabrication route.