Fuel tank replacement job

Add my thanks for the ongoing progress reports on this arduous but important job; one of the most fascinating threads I've read (even the whiskey reviews!). Well done on both the job and the continuing updates! It caught my interest because I'm facing removing an ancient badly corroded steel tank from a 1979 motorsailer.

One thing I didn't see in the thread that I've been worrying over is purging the tank of residual diesel fuel and fumes before attacking it with a saw or cutoff wheel; rather not blow myself up from a spark. How did you do that...or I am worrying unnecessarily?

CapeWhaler said:

Add my thanks for the ongoing progress reports on this arduous but important job; one of the most fascinating threads I've read (even the whiskey reviews!). Well done on both the job and the continuing updates! It caught my interest because I'm facing removing an ancient badly corroded steel tank from a 1979 motorsailer.

One thing I didn't see in the thread that I've been worrying over is purging the tank of residual diesel fuel and fumes before attacking it with a saw or cutoff wheel; rather not blow myself up from a spark. How did you do that...or I am worrying unnecessarily?

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I cut a large access hole and cleaned out all the sludge. I then sprayed degreaser and wiped it out. I only used a saw all with agressive carbide blades. I would not use a cutoff wheel. Too many sparks and too much heat. I never saw a spark and it didn't heat the steel because it chipped the material out.
Good hunting?

At room temperature diesel is amazingly hard to ignite. When we had a fuel tank replaced, they drained it then cut off the top with a sawsall. There was still about 15 or so gallons of diesel in the tank that would not pump out thru the pickup tube. Then they scooped out the diesel and crud and finished cutting up the tank. We have tried to ignite diesel for a fire fighting training exercise. Used a road flare and it would not ignite. After we tried everything we could think of we finally put about an ounce of gas in the diesel and it went up with a match. After it was ignited the first time and extinguished it would relight easily since it had been heated up.

Thanks for the feedback. I understand that diesel fuel is hard to ignite at normal temps, have been mainly concerned about the buildup of fumes in the tank (believe the tech term is 'ullage') and the potential for that igniting from a random spark.

Not to digress into a long background story but I was close to the TWA flight 800 investigation where the fumes in a nearly empty fuel tank exploded from a stray spark, diesel and jet fuel being close cousins. In that case the plane had been sitting all day in 90+ temps, 'boiling' the residual fuel. Maybe my answer is to use a Sawsall carefully on a cold or cool day to open an access to the tank and clean it out as Fryedaze suggests.

Thanks, guys.

If you are concerned pump a co2 fire extinguisher into the tank before cutting. Watched a fellow cut many empty auto gasoline tanks up with a cutting torch using this method. From a distance I may add.

Hadn't even thought of that. Good suggestions - thanks.

CapeWhaler said:

Hadn't even thought of that. Good suggestions - thanks.

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I know one person who dropped a bunch of dry ice in the tank before starting. After a while the tank would be flooded with CO2.

Be careful! You don’t want your confined space (engine room) filled with CO2. It’s much better to have oxygen!

Time to start the port side. 5 years ago I ran this post to show my stb tank replacement. At the time I thought I would do port the next year. I procrastinated and now I am cutting it out. I got a little push after I took on fuel with a high speed pump and the pin holes in the tank top leaked.
Day one was interference removal. Hot water heater and potable water pump removal. Engine coolant was removed and the expansion tank removed.
Day 2 was fuel transfer to stb tank, about 75 gal. Fuel tubing and Raycor removed. Forward end of tank opened and sludge removed. Sludge was an inch deep in this section.
Work was cut short because my Makita sawsall crapped out. It's 35 years old. Two days in and 9 man-hrs so far.View attachment 140448View attachment 140449View attachment 140450View attachment 140451View attachment 140452

Sludge video. 33 year old boat. 13k gallons of fuel through this tank. The tank has three compartments. This one has the fuel return.
Video link for sludge

https://youtu.be/Hz7hPnjuis4

No disrespect for you guys but if I were doing the job I'd fit custom built stainless steel tank with bright annealed interior finish with a drain at the bottom at the lowest point for your fuel supply. You never see a truck tank with that crap in the bottom as any sediment is automatically removed by your primary fuel filter, they get changed at regular servicing so no build up of crud to be agitated in rough seas. Put a 'T' piece at the drain and once every month draw off a glassful to check if there's any water.
On top of the tank I would fit an oblong removable plate bridging your baffles and bolted down with your return pipes plus and heater pickups and your fuel gauge sender. In the unlikely event of any crud (which I very much doubt) you can remove the oblong plate and hoover it out.
The advice i give is experience from running a tanker trucking business for 30 years.
Do it once, do it right, quality is remembered long after price is forgotten.

Day 3 Tank removal complete

The other two compartments also had rust scale sludge. the last compartment with the fuel pick ups had the most. Probably due to particulate being pulled to it. The top of the tank was riddled with holes near the fill and vent. I patched this area with Marinetex in 2015. You can see in the picture where it lifted off the steel. All the hard work is done. Tomorrow I will rest and heal and I will be making my drawings and submitting to SP Tanks in Jersey. They made my stb tanks and I was very pleased with the quality and price. We will see how it goes 5 years later.

3 days,16 hrs, one old guy. 7 hrs interference removal and 8 hrs cut up and remove. A good thing to remember when the boat yard quotes $15K to replace your fuel tanks. The only reason I let go of a dollar bill is to get a tighter grip on it.

fryedaze said:

The other two compartments also had rust scale sludge. the last compartment with the fuel pick ups had the most. Probably due to particulate being pulled to it. The top of the tank was riddled with holes near the fill and vent. I patched this area with Marinetex in 2015. You can see in the picture where it lifted off the steel. All the hard work is done. Tomorrow I will rest and heal and I will be making my drawings and submitting to SP Tanks in Jersey. They made my stb tanks and I was very pleased with the quality and price. We will see how it goes 5 years later.

3 days,16 hrs, one old guy. 7 hrs interference removal and 8 hrs cut up and remove. A good thing to remember when the boat yard quotes $15K to replace your fuel tanks. The only reason I let go of a dollar bill is to get a tighter grip on it.

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Good job! Great feeling of accomplishment I am sure.

Cigatoo said:

Good job! Great feeling of accomplishment I am sure.

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Yep, I will be happier when the new tanks are full and she's not listening anymore.

Wow, I think you are doing great. Keep up the posts as it is very interesting.

Don't worry Frydaze most of us 'old hands' have been there at some time or other in our boating lives. You certainly can save a lot of money and the satisfaction of having a job well done beats all the aches and pains. Just keep to the one standard, perfection ! When I did mine I got lots of advice but just kept plugging away. Just for your info I bedded my new tanks in with an aerosol of expanding polyurethane foam, it stabilizes the temperature to reduce condensation and cuts down any noise echo from a part filled/empty tank.
Don't get too set in your ways, think out of the box a little, when the days work is done why not try a gin & tonic with some ice and a slice of lemon, or if you prefer lime .
Saving all that money doing it yourself is great. Are you sure you are not from County Antrim in Ireland ? We're noted the world over for having short arms and deep pockets !
Good luck with the work.

fryedaze said:

Yep, I will be happier when the new tanks are full and she's not listening anymore.

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Listing

Wow, keep posting through the replacement. Your doing a great job dealing with something most boater have a deep seated fear of. 16 hrs sounds like great progress to this point.
Hollywood

Fryedaze,
Listening ? Are you referring to the constant advice you kept getting from the Admiral ? ?
You are not alone my friend, we all have one of those

Irish Rambler said:

Fryedaze,
Listening ? Are you referring to the constant advice you kept getting from the Admiral ? ?
You are not alone my friend, we all have one of those

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The Admiral helped with tank removal back in 2018. After that she told a story to everyone about how dangerous it was and that I wasn't allowed to do the other side. I should pay someone to cut the tank out. Well, it isn't dangerous, it's just very loud. Needless to say, I had her stay home this time. I didn't want to hear how terrible it was for the next 5 years again.[emoji23][emoji23]

Sensible man Frydaze.
When you've finished work and having a glass of 'relaxation', she won't be there to count them either !
Good Luck with the job.
Enjoy the 'relaxation' afterwards.

Today was mock-up build. Last time I used a wood frame and styro board. It took most of the day. This time I used cardboard and styrofoam blocks with hot glue. It took 2.5 hrs and made for a better mock-up. Did the test today getting through the door with 1/8" to spare after removing railing and a stanton. The ER clearance is about 1/4". The fabricator can't make any mistakes. I will be signing the contract with SP tanks Monday. The estimate is 74% more than 5 years ago when I think I got a smokin deal .

Good plan.

I also added bumps to my mock-up to simulate the connections - just to be sure !

Nick F said:

I also added bumps to my mock-up to simulate the connections - just to be sure !

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Good idea. My connection tank penetrations are all flush welded threaded bungs. When I installed the first set of tanks I forgot to install the two pickup tubes. I had to cut 3" holes in the floor of the seatee locker. This time I can tilt the tank forward and thread them in.

I didn't want to hijack this thread however the following process may be of help to save your fuel tanks. Hopefully not too little too late for me?
https://www.trawlerforum.com/forums...ng-water-top-fuel-tank-68819.html#post1183493

New tanks have been ordered from SPtanks out of Jersey. Cost was just under $1800 for two 77 gal tanks 5 years ago. This time they will cost $3k. Delivery is 7-10 bus days. Looking forward to wrapping this up in few weeks.

Well compared to having it done by a yard the cost isn’t that bad. Let us know how it goes.

Are you replacing one tank with two? What was the capacity of the original tank(s). Loss of capacity and the convenience of one vs two tanks seems to be the only downside to such a replacement strategy. Seems like a worthwhile tradeoff.

twistedtree said:

Are you replacing one tank with two? What was the capacity of the original tank(s). Loss of capacity and the convenience of one vs two tanks seems to be the only downside to such a replacement strategy. Seems like a worthwhile tradeoff.

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I cut out a 175 gal single tank and will replace with two 77 gal tanks tied together.
Check out post #96
After this replacement we will have lost approx 100 miles out of our 770 mile cruising range. I don't think we have ever gone past 550 miles before fueling.