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Fuel tank Replacement turned into more!


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        Well...this is gonna be a long thread....it started as a faint smell of gasoline. I tried to find the source with a bore scope inspection camera....no good! So I finally cut a large hole under the front seat of the console, that let me get into the front of the tank area better but I still could not find it. So next I knew of a material/kit called "POR 15" which a lot of restorer's use to fix leaking gas tanks on cars and motorcycles, I thought it was worth a shot before cutting the deck to get the tank out.

       So after cutting two large holes (7" round) into the front and aft ends of the tank to allow me to get inside, I cleaned and prepped it to the instructions in the kit. After cleaning and phospho-tizing the inside I sprayed the sealant all around the interior...top bottom, sides and interior of the center section between the baffel's...everywhere! After four days of drying I put 8 gallons of gas in it and after two days no smell! I got brave then and put 40 dollars worth in it...bad Idea. The tank started leaking again because now the fuel was back above the hole! New Plan.....drain all the fuel again and figure out where to cut the deck at to get the *** thing out!

       The pictures below show the tank after getting it out and after the sand blasting to get a look at where it was leaking. Then I found stringer problems! When I first bought the boat it was a Boca Grande guide boat...I figured it had some hard miles on it but for 8K I bought it anyway. I found that the port stringer was separated from the hull at the transom and repaired that, it had a small hole in the port front side below the shark eye light that someone had put some "Kitty Hair" fiberglass putty in to seal it up. I wanted to fix it a little better so I cut the bottom out of the port storage locker to get at it. I found the front 6 inches of the port stringer popped loose fight behind where to hole was punched. I have no idea what they hit but it must have been big and hard! I got that all glassed back in and have been a happy boat owner for about 9 years.

     Now back to the bad tank, after looking it over after the sand blasting it had the salt water cancer bad! So I called the original Mfg from their label on the tank, they are still in business and after looking up the drawings for the tank( it is not in production any more) they gave me a price of $771.00 for a brand new one without a sending unit, I bought a new one when I started the sealing process. I ordered it! no second thoughts....

      So for the past three days I have been cleaning the bilge, sanding and prepping all the cracks and splits under the port stringer and today I puttied in all the areas where the stringer had broken loose from the hull to give a smooth transition from the stringer to the hull to make a nice radius for the glass. I filled all the cracks with cabosil/epoxy putty sanded them smooth and epoxied three or four layers of 1708 biaxial glass into all the bad places over lapping 4 to 6 inches back onto the old parts to reinforce it all probably 100% more that original. The white you see under the glass repairs is the putty to make the radius and patch the cracks. The epoxy has more bonding grip to old glass than doing this with polyester resin that the hull was built with originally. You can see all of the repairs in the pictures  and I will post some more if anyone is interested.

       I'll get the new tank in three weeks and will update after the install and putting the deck back together....whish me luck!














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Nice work!  I have a 1998 21 MA.  It had a tank done in 2010 and had a similar repair done on the front port side.  They cut the locker liner out to access it.  The 21's are beasts, but I think people push them farther than they should since the ride is so good.  She should be much stronger with the repair you made. 

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Great thread for those of us with older tanks. I have 18 not 21 but obviously that is all you had to cut to get it out? By chance do you have a full overview pic? I know often some folks take the entire cap off so just wondering/curious what I am facing and how to get it out when its time comes as mine is older than yours. 

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            I will put up some more pictures....I have lifted to cap before to get at the port stringer in the front and to repair the flare at the top port side where the troller sits. The entire "L" shaped lip where the cap meets the hull was broken on the hull side from the bow back about 6 feet...almost to the fuel fill. I made those repairs about five years ago when I mounted a new trolling motor and discovered it. When pulling up the cap on a 21 it lifts fine till you get to the rear of the cockpit, then it does not want to come up anymore, which means the bow deck is only about15 or 16" gapped open, not enough to work the tank out thru that way.

            So cutting the deck out is the preferred way to do it after many hours of YouTube watching. Taking the cap off is not so easy, the hull and deck are glassed together at the transom, not where you want to be cutting unless you have to, the section I cut out is not structurel. I will epoxy a bunch of 4" x 8" tabs all around to hole after I install the tank and epoxy the cut out from the deck on top of them also back filling the gap with epoxy putty made with Cabosil & resin, then feather back the glass and gelcoat back 2 or 3 inches on either side of the cut line and build that back up with multiple layers of cloth and epoxy. Then I will sand the entire cockpit and roll on new gelcoat with no-skid in it.


             The foam on top of the stringers in my boat is encapsulated with glass & polyester resin, then they put about 1 1/2" of putty on top of it and join the cap to the hull. Mine is still intact, foam and putty and still supporting the deck. That is one reason I cut the hole in the deck only 1" wider than the tank, I wanted to leave enough room on either side of the hole to glass the future tabs to support the rejoined deck. I stuck my phone in under the deck many times taking pictures and making measurements before pulling out the skill saw....LOL. Also, if you look close at the picture of the big crack repair in the upper RH corner of the photo you can see the glassed in foam sitting on top of the stringer with a second layer of foam on top of that one and then the putty to support the deck is out of the frame.

             I am also taking this time to fix up some gel coat chips in the hull and deck....boy is that stuff expensive! I paid $158.00 for an pint of gel coat putty color matched to the Oyster White on my hull. With wax added and the peroxide hardener.....glad I did not need a gallon!                    Mini Craft in Wildwood, Fl.

               Probably three weeks till I get the tank.....at least it is almost to hot to fish... :( 




thumbnail_IMG_2543.jpgFoam stringer and deck support up top right


thumbnail_IMG_2558.jpgSexy from this angle

thumbnail_IMG_2559.jpgHole- 23" x 78", tank 22" x 86"

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  • 2 weeks later...
  • 3 weeks later...

Well...it's all done....& turned out pretty good if I do say so.

       I kinda surprised myself on this, the over all plan worked out just as I had hoped, and putting in the SeaDek was a good thing even though I really did not need it to hide my glass work. It was a lot of work, good thing I retired last year or I would have had to pay someone to do this. I learned these skills starting out of high school helping my room mate refurbishing & painting old trucks and cars to flip. He had been doing it for a few years before I met him, and I also started buying old boats and fixing them up, learning the fiber glassing trade doing that. So my back ground really paid off this time. So other than itching for three weeks this was a pretty good adventure. I also to this time to fix up some nicks and dings along with old screw holes with gelcoat & cutting in some new cup holders. Here are the last of the photos, enjoy!







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Very nice work.  Glad to see her buttoned up again. 

Unfortunately my boat will be going under the knife here very soon.  I have a 1998 with the front sea chest grate under the front well.  One of the thru hull fittings broke off and actually pushed thru the liner in the starboard rod locker.  It was obviously flooding the bilge.  Whatever holds the cap and liner in place is loose which allowed the liner to move and hit the thru hull fitting.  Its either a bulkhead, stringer or both.  I will be cutting the entire floor out and removing the tank in order to get access to the front of the boat (Pulling the cap is not an option).  I will post some pics as I start the process.   

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15 hours ago, Lap it Up said:

Very nice work.  Glad to see her buttoned up again. 

Unfortunately my boat will be going under the knife here very soon.  I have a 1998 with the front sea chest grate under the front well.  One of the thru hull fittings broke off and actually pushed thru the liner in the starboard rod locker.  It was obviously flooding the bilge.  Whatever holds the cap and liner in place is loose which allowed the liner to move and hit the thru hull fitting.  Its either a bulkhead, stringer or both.  I will be cutting the entire floor out and removing the tank in order to get access to the front of the boat (Pulling the cap is not an option).  I will post some pics as I start the process.   

Lap, is that an MA?

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  • 2 years later...
On 8/1/2019 at 6:12 PM, bdsnook said:


       Yes I had two of the cross braces between the stringers cracked also, but no hull breach's, the pictures were in the first batch.

  The new tank got finished ahead of time, I picked it a week ago, I coated the outside after cleaning and sanding it a little with the remaining quart of the POR15 gas tank sealer I had leftover from the patch attempt. Fitted my new Bosch fuel sending unit into it's new home and wiggled the tank back into the hull. Instead of foaming it in like the factory I used polyurethane caulk to stick 3/16" BUNA N gasket material to the cross braces that the tank sits on and screwed it down on the end tabs. I had reinforced the area where the screws go with more glass & resin. Then I cut some 1" thick Delrin (think thick nylon) and adhered more Buna N to one face and shoved them into the gap between the stringers and the tank, no way for it to slide side to side now. Everything that the tank touches is now faced with the Buna N to cushion it and it will not absorb salt water!

Then after connecting all the fuel hoses and sending unit I began epoxy bonding tabs all around the opening to support the deck plug I cut out. The tabs at both ends where you step down into the cockpit from the front or back casting decks were made out of 3/8" G10 epoxy board, extremely tough stuff....very strong. I figured those areas would have to take a lot of pounding from stepping down all the time. All the remaining tabs I built out of hard foam board wrapped with glass cloth and resin, after bonding to the underside of the deck I could put my full weight on any of them and they did not budge.

I then installed the cutout, there was a 1/8" gap all the way around from the saw blade used to cut the deck, I purchased an injector from Walmart meant for juicing up a turkey and filled it with epoxy resin mixed with Cabosil to thicken it. The included needle on the syringe fit the gap perfect and I squirted the gap full all the way around filling it up. After that set up I commenced the fun part....grinding a 4" wide concave strip all the way around the plug centered on the gap....2" to either side and almost all the way thru the old glass to the honey comb deck core...but not all the way thru. The concave area was layed up with three layers of glass cloth, 1" wide, a 2" wide and last a 3" wide strip, wetted out and rolled out.

Tomorrow I will sand that all flat and gelcoat the entire cockpit to seal the new glass work. Next week I have two sheets of SeaDek coming and I will cover the entire cockpit with it then install the console and reconnect all the wires, cables, hoses to get me back in the water!      Whew!!!!


thumbnail_IMG_2567.jpgShe Fits!

thumbnail_IMG_2599.jpgGlass work next to the rear deck

thumbnail_IMG_2598.jpgFront deck step down area

thumbnail_IMG_2576.jpgfitting it up, ready to fill the gap

thumbnail_IMG_2597.jpgWide Shot!

thumbnail_58489521371__81CCF6C6-4304-4A2C-88BA-9290EE961F10.jpgDeck core close up

thumbnail_IMG_2564.jpgA thing of Beauty!

thumbnail_IMG_2573.jpgTabs, light green are G10, others were home made


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