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Old 01-30-2014, 11:16 PM   #21
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Originally Posted by kulas44 View Post
It would have taken a week and an incredible number of blades to cut the 400 gallon side tanks out of my trawler. The 250 gallon tank under the floor midship required the complete dissassebly of the boat in that area. Both enterior walls and the sole had to be removed just to get to the top of the tank. We then cleaned it completely and cut it apart with a oxy/acetilyne torch. All of these tanks were 1/4 inch "black iron, aka just plain mild steel. The lower tank had a small leak that was repairable and the side tanks did not leak. No way could I not change them out and sleep well at night. I will not refit a boat just to redo my shortcuts later. I like poly tanks just fine but they dont come in the sizes I needed and are not baffled. I did not want to reduce my tankage, preferring to increase it, substantially if possible. All were replaced with custom built 5086 1/4 in aluminum to commercial specs and installed correctly. I cant imagine how much this would have cost in a boatyard, well over $50,000 if done my way I'm sure. But it is done correctly and will not need redoing in my, and probably the next owners lifetime. Tankage on most boats constitutes a major expense if they need work, no way around it. Poly tanks are a good stop gap measure. Patches and epoxy lining work to. Just not for me. While the engines were out of my 48 sportfisher I removed the fuel tanks "just to look" and found a small area on the 350 gallon mid tank about the size of a dime that was corroded about 1/8 inch deep. It was cut out and repaired. They had not previously leaked but had I not removed and looked at them they would have been leaking eventually. I also installed 12x12 clean out/inspection plates in every baffled section, all in all a total of 16 in two tanks. Now cleaning them is easy. I coated the tanks with coal tar epoxy and installed them on 1/2 thick rubber strips. I documented the process, with pics, just in case the next owner wants proof of the work done, in both cases. Non of this was easy or cheap. I knew when I bought the boats exactly what I was going to do so I was not surprised, it was just part of the deal. I strongly suggest anyone buying an older boat look at tank replacement as "probable" and proceed with that in mind.
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Old 01-31-2014, 12:15 AM   #22
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Boatpoker, try the "Thanks" button , not public, but gets to the right place.
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Old 01-31-2014, 06:29 AM   #23
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Every boat and situation usually is a little different...that's why I made my posts ...to show SOME of the people it may be no big deal for some boats or their situation...but tank removal or replacement IS NOT NECESSARILY THIS -

post #18 - "30 year old rusted or corroded tanks on a trawler are a REALLY BAD DEAL. Unless the boat is really cheap and you really like it, run ,run, and run faster"
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Old 01-31-2014, 08:06 AM   #24
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Every boat and situation usually is a little different...that's why I made my posts ...to show SOME of the people it may be no big deal for some boats or their situation...but tank removal or replacement IS NOT NECESSARILY THIS -

post #18 - "30 year old rusted or corroded tanks on a trawler are a REALLY BAD DEAL. Unless the boat is really cheap and you really like it, run ,run, and run faster"
I agree. A big project perhaps, but no bigger than many other possibilities on a used boat esp if you are a do-it-yourselfer.
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Old 01-31-2014, 08:49 AM   #25
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That is correct, just assess the situation and if tank removal is problematic, look elswhere. Even if there are no leaks now, most older metal tanks eventually will leak. If you can "fix" the problem yourself to your satisfaction, or have a yard do it for a price that you are ok with then dont consider it a deal breaker.
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Old 01-31-2014, 09:03 AM   #26
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It's funny...this discussion is exactly why I have little love for many production boats.

Skipperdudes philosophy is aligned with mine..."If you can't repair it maybe it shouldn't be on a boat"....

I'm not that much of a purist...but when I eyeball a boat...I look for inaccessible systems or difficulties in removing large objects like gensets, engines, tanks, etc....

Every repair I make, I usually leave it easier to repair or troubleshoot the next time.

So kulas44 please don't feel like I'm slamming your concept as I might walk from a boat with inaccessible tanks, even if they were in good shape. I'm just saying that every boat and owner has a different set of priorities....and my situation made removing my tanks a priority yet just another one on a long list of projects.

Heck, some of my boating friends don't even need fuel tanks in their boat...they would just get e to tow them to/from their slips if it were allowed...
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Old 02-01-2014, 01:24 PM   #27
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The PO replaced the black iron tanks on my 1985 KK42 with aluminum tanks. He did the re and re work himself but had an outfit in Bellingham build the tanks. The PO maintains boats for a living and the work looked very well done, but I guess time will tell, as with all things. He also put in a fuel polishing system. This is what it looks like now.
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I should say that cutting out a tanks is a tricky process. I had an above ground oil tank removed. The fellow who did the work used a heavy duty grinder to cut it apart. He had a major fire going on inside the tank. Glad I wasn't doing it! Not what you want to have on a boat!


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Old 02-01-2014, 01:37 PM   #28
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boatpoker,

A lot of guys post;

"+1 "
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Old 02-01-2014, 01:45 PM   #29
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The PO replaced the black iron tanks on my 1985 KK42 with aluminum tanks. He did the re and re work himself but had an outfit in Bellingham build the tanks. The PO maintains boats for a living and the work looked very well done, but I guess time will tell, as with all things. He also put in a fuel polishing system. This is what it looks like now.


I should say that cutting out a tanks is a tricky process. I had an above ground oil tank removed. The fellow who did the work used a heavy duty grinder to cut it apart. He had a major fire going on inside the tank. Glad I wasn't doing it! Not what you want to have on a boat!






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That's why I used a recip saw...no sparks, no appreciable heat...may have taken longer than a grinder, but with minimal ventilation, the saw was perfectly safe as the was no atomized fuel and it was at or below room temp.
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Old 02-01-2014, 03:58 PM   #30
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What's the downside to plastic? Other that the obvious soldering iron or welder's torch.

So far all I've heard is no baffles.
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Old 02-01-2014, 04:06 PM   #31
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Bay Pelican's two 350 gallons tanks were cut up in place without removing the main engine or generator. Replaced with four 120 gallon aluminium tanks. Everything else in the engine room forward of the genset had to be removed. Process took 5 weeks and $22000 US.

My general comment is that if you are buying a 20 year old boat with steel tanks that have not been replaced you will get to replace them. Don't know about other materials.

As far as tankage is concerned, few of us need the original 700 US gallons on a Krogen 42 and thus the smaller multiple tanks.
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Old 02-01-2014, 04:12 PM   #32
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My 58 gallon plastic tanks have baffles in them.

I went smaller because I knew I would never need to steam 1200 miles without refueling. Even with a little over 100 gallons I can still easily go 300 till fuel-up with reserve.
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Old 02-01-2014, 08:22 PM   #33
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My trawler is a 50 foot Krogen design, 1972 model. I wanted to increase tankage as much as possible, and the originall tanks were 1/4 inch thick steel, a leak waiting to happen. Removal was VERY labor intensive and exceedingly intrusive. I went with 5086 aluminum but if I had it to do over I would build from fiberglass directly into the hull structure for added strength. I am not aware of any roto molded poly tanks with baffles, especially in the size and configuration I needed, or baffles in any size poly tank for that matter. This boat is currently being refitted (read completely rebuilt) with world cruising in mind. Fuel capacity now is about 1000 gallons. I'm planning to add about 500 gallons under the cockpit sole. I would like to have a 4000 mile range with 10% reserve. This will not be a coastal cruiser. As such "good enough" is just not what I am interested in. My goal is a boat than can handle a knockdown and get back up. Large fuel tanks are a serious issue as pertains to that. Free surface affect is a big deal. The ability to take on fuel, clean and process it thru a high capacity polishing system is also important. But, there is always the possibilty that I am addicted to overkill. After all, how many times does a power boat get knocked down. The answer is "usually just once"!!!!
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Old 02-01-2014, 08:40 PM   #34
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My tank has a hole molded through the center of the tank and acts like any other baffle...it's a great idea and all you need on a small tank like mine...

Works well so far ....as in some pretty good pitching conditions the tanks didn't slide at all so I'm satisfied the free surface effect was definitely diminished. The have about an 1/8 of an inch to slide as I had to make the stops a tad wider than the tank as they say the plastic tanks grow a bit when first filled with fuel.
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Old 02-02-2014, 07:12 AM   #35
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The downside of plastic for boat assemblers is time and hassle.

The plastic tanks expand when filled with fuel, so must be put in place , filled with fuel, allowed to expand , and then properly fastened usually also foamed in place .

Then the fuel ir removed and the next batch of tanks installed.Labor time is money .

Baffles can be done , but usually the tanks are sized so the head pressures caused by boat motion is low.

Biggest problem with plastic is they are simply a box of fuel, not a fuel tank.

This is OK if the setup allows the unused tanks to be drained during small fuel requirement operation.

All will work better with a dedicated day tank, so water and gunk can be drained from the bottom.
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Old 02-02-2014, 10:07 AM   #36
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Not that I'm looking to replace my two (orig 1977 and very dry of water in & out) apparently good condition 100 gal aluminum tanks anytime soon (fingers doubly crossed!)

But...

What I've read previously as a simple remedy for tank removal is suction:

I've seen mentioned (not on this thread) that HD suction machine considerably collapses tanks inward so they become less cu ft dimension and can then be more easily maneuvered out of their location.

Any knowledge / input on this technique? Sounds as though it could be a relative slam dunk for tank removal of relatively foldable thin walled tanks... e.g aluminum! 1/4" thick mild steel might not be too conducive to using this method

Of course if they are gasoline tanks then fumes would need to be made non explosive by displaced air in tank with inert gas/vapor having NO oxygen.

Just wonderen??
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Old 02-02-2014, 10:28 AM   #37
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Greetings,
Mr. Art. Hmm....Sounds good but....what if the tank collapses in a non-symmetrical fashion leaving awkward angles difficult to approach with a cutting device. I don't think one could achieve complete collapse before springing a vacuum leak. Could be creating more work than starting with plumb, flat surfaces.
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Old 02-02-2014, 01:31 PM   #38
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Not that I'm looking to replace my two (orig 1977 and very dry of water in & out) apparently good condition 100 gal aluminum tanks anytime soon (fingers doubly crossed!)

But...

What I've read previously as a simple remedy for tank removal is suction:

I've seen mentioned (not on this thread) that HD suction machine considerably collapses tanks inward so they become less cu ft dimension and can then be more easily maneuvered out of their location.

Any knowledge / input on this technique? Sounds as though it could be a relative slam dunk for tank removal of relatively foldable thin walled tanks... e.g aluminum! 1/4" thick mild steel might not be too conducive to using this method

Of course if they are gasoline tanks then fumes would need to be made non explosive by displaced air in tank with inert gas/vapor having NO oxygen.

Just wonderen??
Sounds interesting but if the tanks are being replaced due to corrosion/leaks it won't work !
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Old 02-02-2014, 04:50 PM   #39
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Greetings,
Mr. Art. Hmm....Sounds good but....what if the tank collapses in a non-symmetrical fashion leaving awkward angles difficult to approach with a cutting device. I don't think one could achieve complete collapse before springing a vacuum leak. Could be creating more work than starting with plumb, flat surfaces.
RT - True, True!

However, what I heard was to take out all easily removable adjacent structures and use a really big, high cfm suction machine (rented unit). Tank quickly collapses to 50% or less of orig size. Might or might not work?? If need to remove our tanks ever become needed... suction collapse is one technique I will closely look into. Be worth it to find some old tank at marine yard and do a test first to see how well that technique actually works. Could be inexpensive and fast tank removal process!
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Old 02-02-2014, 04:54 PM   #40
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Sounds interesting but if the tanks are being replaced due to corrosion/leaks it won't work !
See post # 39! High CFM big rig... Small leaks should not be much detraction to "suction collapse"!
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