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Old 07-26-2016, 08:35 PM   #1
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City: New Haven
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Vessel Name: Chesapeake
Vessel Model: Mainship 30 Pilot II
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SS screw in aluminum diesel tank

The stainless steel screw that attaches the chain that holds the diesel cap came off and fell into the fill tube. My Mainship Pilot has aluminum tanks. Any worry? Same thing happened with my previous boat but it was the water fill, not a big deal. Kicking myself for not tightening them.

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Old 07-26-2016, 08:50 PM   #2
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Worth trying a magnet, some grades of stainless screws are magnetic.

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Old 07-26-2016, 08:51 PM   #3
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All my fittings in my aluminum Fuel tanks are aluminum.

SS and aluminum create corrosion but some boat builders use SS fasteners in aluminum boats.

With some SS alloys and some aluminum alloys certian combinations may be OK but generally no.

North Western Washington State USA
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Old 07-26-2016, 10:25 PM   #4
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I wonder if some borescopes are safe to lower into diesel. If so, you could probably see the screw and perhaps get it with a "claw" picker. I keep one of the pickers in my engine room for the occasional dropped bilge rat.
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Old 07-26-2016, 11:51 PM   #5
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So in general those two dissimilar metals would be a no-no together. However, petroleum products are generally poor conductors so the thin layer between the washer and the tank bottom would act like an insulator and reduce the electrolysis. Of course, any dirt or water in the tank would increase conductivity.

Do you think it's worth the effort to retrieve it?

I once dropped a washer into the bowels of my diesel. Wild nightmares ran through my mind of the engine blowing up. However, short of tearing it apart there was little I could do, so I did nothing. Engine kept purring along.
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Old 07-27-2016, 07:58 AM   #6
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I agree with Mako. I wouldn't worry about it.
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Old 07-27-2016, 08:45 AM   #7
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If your tank has removable inspection ports, open them up and clean it out before your next fill up. It would bother me more psychologically that it was there far beyond any rational reason to remove it as it will likely be happy to live there for the life of the boat.
Craig - AKA Some Clueless Idiot

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Old 07-27-2016, 08:53 AM   #8
City: Carefree, Arizona
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No worries sounds good but Al and most SS are not a good mix when looking at the compatibility charts. Assuming you have little water in tank bottom and SScrew jostles around it will be cannon fodder 35 years from now on TF for some poor bloke who wonders why his tank has pin hole leaks.
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Old 07-27-2016, 10:47 AM   #9
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Ooooh, awful memories bubbled up! I had the fuel tank out of my '53 Studebaker back in 1969 (while I was welding on the body back there). I stuck a pencil in the exit tube (to keep dirt out, you know). I broke the thing off as I went to put the tank back in. I reassembled the tank anyway thinking it unlikely that the broken tip would ever cause a problem. The very next time I drove the car, it went about 20 miles before it quit. Got down, got under, removed the rubber fuel line, pushed a wire in and dislodged the point...and, five more times to return to base.

Your screw won't do that, nor cause any other problem, I think.

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