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PostPosted: Sat Apr 11, 2009 5:26 pm
by mike
Cars,

I would go exactly with what you have said, if the previous elbow didn't get hot & you have replaced it with a custom unit you have to assume that there is possibly something not quite right with the internal design of the new riser/elbow.

mike

PostPosted: Tue Apr 14, 2009 5:44 pm
by Scout
Sorry for taking a little time to get back to you. Thank you for your continuing interest and help. As for your logic, I follow it completely and must concur with your approach. As for items changed, that includes ONLY the following: (1) material of the riser (design taken from prior one); and (2) possibly the volume of wrap material used. The prior elbow was like welded piping with threads on the exiting end. I suspect that the volume of wrap was more previously. In fact previously they wrapped the entire elbow which I have not done; and (3) now that I think of it, they used like a monel wire to hold the wrap material in place, which I have not done. I used some high temp exhaust sealant (silicone like material).

My current intentions is to try to spread the diameter of the exhaust hose some to accommodate additional wrap under it and see if that works, plus to put some wrap under the SS clamps. It is spring and the weather here is awesome, so it is time to get out and I will see how that works.

Any additional comments or tips will definitely be appreciated.

Thanks, Scout :)

PostPosted: Tue Apr 14, 2009 5:58 pm
by mike
Scout,

I don't think you are addressing the real problem, there should be no need to put some wrap between the elbow & the exhaust tubing, it shouldn't be getting that hot on the outlet side, the injected water should be keeping it cool. I still personally think the problem is with the construction of the elbow in particular its internal design which isn't letting the cooling water do its job.

mike

PostPosted: Tue Apr 14, 2009 10:21 pm
by warmrain
Ditto what Mike said,

Wraping the elbow under the exhaust hose is unwise and probably against ABS guidelines and Coast Guard regulations. Additionally placing material under the hose clamps seems unwise if not also against regulations... any of these kludges could result in exhaust leaks or the complete failure of the hose to remain on the fitting.

The original exhaust fitting design is designed as I described above and is internally cooled by injecting water on the engine side of the riser in an internal baffled chamber. If the design was based on the prior one... was the prior one an original design? If it was, there still is not a guarantee that it is internally of the same design. If it was based of a previous one that was not the original one (i.e. a copy) it may not have been a proper copy.

Beyond the design... you are correct, the material is different. However consider all the properties of the different materials. For example a cast piece of iron is very thick and it a big heat sink that is able to absorbe a great deal of heat...

If what changed is the elbow... then the elbow is the problem. If you kudge it then you have multiple opportunities for failure...

~Cars