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Author Topic: Inside a 1987 Fuel Tank  (Read 318 times)

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Jon W

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Inside a 1987 Fuel Tank
« on: April 20, 2019, 02:34:04 PM »

I've been planning to remove and clean the inside of my diesel tank since I bought it in 2015. With the recent posts on tank leaks, I decided to move this to the top of the project list to not only clean but also check the condition of the aluminum. To get into the tank, I cut holes in the top for 2 8" access plates I bought. The attached photo's are what I found.

The first photo is inside the forward end of the tank. The silver tube is the new fuel pick up I put in when I removed the OEM hose and strainer. It turns out what I removed wasn't the original. As you can see the original was still laying in the bottom of the tank along with a float from an old level gauge sender.

The second photo is the baffle inside the tank looking forward. I've read where folks said they cleaned their tank by pressure washing without top access plates, but don't see how they got by the baffle.

The third photo is the pile of old growth I removed from the bottom of the tank today after soaking with water and simple green for three days. Those pieces are all a minimum of 1/8" thick!!
« Last Edit: April 20, 2019, 03:51:21 PM by Jon W »
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Jon W.
s/v Della Jean
Hull #493, 1987 MK 1, M25XP, Manson Supreme 35
San Diego, Ca

Noah

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Re: Inside a 1987 Fuel Tank
« Reply #1 on: April 20, 2019, 03:27:04 PM »

Wowzer! Interesting! Lots of junk. What is your verdict on condition of the aluminum? Also, on photo #1 you said “...The first photo is inside the forward end of the tank. The silver tube is the new pump discharge I put in when I removed the hose and strainer...”  Did you mean fuel pick-up tube?
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1990 hull #1014, San Diego, CA,  Fin Keel,
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Jon W

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Re: Inside a 1987 Fuel Tank
« Reply #2 on: April 20, 2019, 03:49:13 PM »

Yes, it’s the fuel pick up tube. I got my gozinta and gozoutta corn fused. I’ll correct it, thanks for catching that.

After a couple hours of scraping with a plastic putty knife, the aluminum looks very good. I won’t know for sure until more cleaning to get a good look at bright metal.
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Jon W.
s/v Della Jean
Hull #493, 1987 MK 1, M25XP, Manson Supreme 35
San Diego, Ca

Bill Shreeves

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Re: Inside a 1987 Fuel Tank
« Reply #3 on: April 20, 2019, 03:59:34 PM »

Do you plan to pressure test it?  A visual inspection is a good start for the obvious but, leaks can come from very small penetrations that may be very difficult to detect by eye.

BTW, I always assumed the baffle would have some holes to permit some flow to the other side.  i guess its flowing along the sides where it may not be welded???   Here it comes...  Baffling!
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Bill Shreeves
s/v "Begnnings" 1987 Shoal Draft #333
M25XPB, Worton Creek, MD

glennd3

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Re: Inside a 1987 Fuel Tank
« Reply #4 on: April 20, 2019, 04:11:46 PM »

Thanks for taking the time to post this. I am a little shocked/amazed at the amount of stuff you scraped out. I have played with out gasoline tanks and they usually are clean. I am assuming this is a diesel fuel issue. I am now a believer if the bio additives.
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Glenn Davis
Knot Yet
1990 Catalina 34 Mk 1.5
Hull 1053
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Magothy River
Chesapeake Bay Maryland

Jon W

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Re: Inside a 1987 Fuel Tank
« Reply #5 on: April 20, 2019, 04:17:10 PM »

The top and bottom corners of the baffle are notched. I suspect the top notches are for venting and the bottom notches are for fluid communication. You can see the bottom notches in the second photo.

A pinhole will generate as the result of corrosion. If I see corrosion I intend to get advice from a welder/fabricator I used in the past. So far I’m feeling very positive about the condition.

As a for what it’s worth- the construction of the tank is a big no no. The baffle and non-formed sides have internal flanges to make assembly easier (read less cost). We used to call these “faying surfaces” The problem in our tanks is the flanges are not “seal welded” so debris can get trapped and then get loose and create contamination problems ie clogged filter. The ability to seal weld in the factory is one reason there should be access plates on the top, another reason is enabling access so the owner/customers can perform maintenance. This is especially true if you’re going to do something as short sighted as put a filter/strainer on the inside of the tank.
« Last Edit: April 20, 2019, 09:25:47 PM by Jon W »
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Jon W.
s/v Della Jean
Hull #493, 1987 MK 1, M25XP, Manson Supreme 35
San Diego, Ca

Bill Shreeves

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Re: Inside a 1987 Fuel Tank
« Reply #6 on: April 20, 2019, 05:26:26 PM »

I didn't notice the corners notched.  Thanks for bringing it to my attention...
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The only thing that always works on an old boat is the owner...

Bill Shreeves
s/v "Begnnings" 1987 Shoal Draft #333
M25XPB, Worton Creek, MD

britinusa

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Re: Inside a 1987 Fuel Tank
« Reply #7 on: April 21, 2019, 12:21:50 PM »

Thanks for posting those pics. I had cleaned out my tank using similar process (simple green) but did not add the access plates.

Here's a pic of the stuff I extracted - just in case anyone needs another nudge to go check their tanks! :)

I know, it looks more like a beach - but it's the swill from the tank in a bucket.

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Paul & Peggy
1987 C34 Tall Rig Fin Keel - Hull # 463

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Jon W

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Re: Inside a 1987 Fuel Tank
« Reply #8 on: April 21, 2019, 12:51:38 PM »

How did you get the stuff loose without access plates?
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Jon W.
s/v Della Jean
Hull #493, 1987 MK 1, M25XP, Manson Supreme 35
San Diego, Ca

mainesail

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Re: Inside a 1987 Fuel Tank
« Reply #9 on: April 22, 2019, 09:10:32 AM »

Jon,

That new pick-up tube looks to be stainless? You really don't want to do this and ABYC actually prohibits it without a form of isolation. Copper, plastic or aluminum are ok, or you can create a galvanic mess.
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Noah

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Re: Inside a 1987 Fuel Tank
« Reply #10 on: April 22, 2019, 11:12:20 AM »

Makes sense. My new aluminum replacement tank from Ezell did indeed come with an aluminum pick-up tube and aluminum threaded attachment “L”  fittings built into tank to thread brass/bronze fuel lines and shut-off valve into. I used Rectorseal #5 threading compound to isolate those threads.
« Last Edit: April 22, 2019, 11:14:23 AM by Noah »
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1990 hull #1014, San Diego, CA,  Fin Keel,
Standard Rig

Jon W

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Re: Inside a 1987 Fuel Tank
« Reply #11 on: April 23, 2019, 02:10:24 PM »

For dissimilar metal corrosion - the tank sits in an always dry area, on a non-conductive surface, and is grounded to the negative bussbar. The SST pick up tube is welded to what I'm guessing is a carbon steel threaded pipe fitting (it's magnetic). When installed the thread sealant provides a level of insulation to the small area of contact between the tank and pipe fitting. After three years of installation, there are no signs of any corrosion on either the aluminum tank flange or the threaded fitiing the pick up tube is welded to.

In the following photos I tried showing the same views of the tank after being cleaned as before to give a before and after. (The pick up tube was removed to be able to clean in that corner). There is some pitting in the bottom of the tank. The worst of which is between the circles from the sunlight. I think that is to be expected after 32 years. The pile of debris grew as can be seen in the last photo. Started to look like the scene inside the house in Close Encounters of The Third Kind.
« Last Edit: April 24, 2019, 08:40:41 AM by Jon W »
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Jon W.
s/v Della Jean
Hull #493, 1987 MK 1, M25XP, Manson Supreme 35
San Diego, Ca

Noah

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Re: Inside a 1987 Fuel Tank
« Reply #12 on: April 23, 2019, 03:33:05 PM »

Although I did not dig into my old tank to 100% determine where it was leaking, before I trashed it and bought a new one: I suspect it was a pin hole(s) in the forward inboard corner of the tank. Below are pics of right after removal, showing area wet with diesel and appearing corroded and then after cleaning that area with a Scotchbrite pad.
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1990 hull #1014, San Diego, CA,  Fin Keel,
Standard Rig

Jon W

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Re: Inside a 1987 Fuel Tank
« Reply #13 on: April 23, 2019, 04:43:02 PM »

The outside of my tank doesn't have evidence of corrosion like that. There are a couple spots in that area on the inside that are worse than anywhere else. Maybe ~10% material errosion. Hopefully cleaning up the inside caught the corrosion in time for the tank to last another 15 years.
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Jon W.
s/v Della Jean
Hull #493, 1987 MK 1, M25XP, Manson Supreme 35
San Diego, Ca
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