slick on starting engine

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John

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Jun 3, 2006
803
Catalina 36mkII Alameda CA
Another question I have: On starting the engine the other day, I noticed a little bit of a black slick on the water which seemed to be coming from the raw water discharge. I felt it and it seemed to be an oily carbon. I never noticed this before, although it might have been happening and I just didn't notice. After about 30 seconds or a minute it stopped. I figure it was an oil build-up or something like that. Is this right? Is it something to be concerned about?
 

Ross

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Jun 15, 2004
14,693
Islander/Wayfairer 30 sail number 25 Perryville,Md.
That is partially unburned diesel fuel that you normally get from the black smoke when starting a cold diesel.
 
Feb 26, 2004
23,023
Catalina 34 224 Maple Bay, BC, Canada
Follow the exhaust gas path

engine to manifold to rw nipple to muffler to exhaust hose and out. Engine off, water sits in muffler. Water is dirty with mix from hot gas exhaust and water at the nipple before the muffler. Engine cold start pushes mixed "stuff" out of muffler. That's all it is.
 

John

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Jun 3, 2006
803
Catalina 36mkII Alameda CA
Thanks for the rapid response. I suspected as much, but I wasn't sure, especially since I hadn't noticed it before. It's probably been doing it, but I just never saw it.
 
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