Installing a second diesel tank

Stops only had a 29 gallon diesel tank which didn’t give her much of a range if we hit a long patch of no wind in the doldrums. Also diesel wasn’t that easy to come by in the south pacific so I knew I needed the ability to carry more. Jerry cans would be an option but I needed to double the capacity of the boat and didn’t have space for a whole lot of Jerry cans on deck. So I started looking into adding a second tank. As it happens I wasn’t using the second head on the boat and didn’t need the holding tank that came with it.

Second holding tank

So my plan was to remove it an replace it with a diesel tank! Easier said than done 🙂

Off the shelf tank that didn’t fit

I tried getting an off the shelf diesel tank to see if it could fit in the space but the hose fittings need to be horizontal 🙁

So the only option was to get a custom made tank to fit in the space. I found a great company (RDS) that would make a aluminum tank to whatever size and shape I wanted. I send them over a sketch with a design that tried to use up all the space I had. They quickly turned that around with a engineering drawing that gave me a max capacity at 23 gallons for the space.

The nozzles to the diesel intake as well as those to connect to the engine were critical to get right. We had a lot of back and forth. Finally it arrived. It was around $520 to manufacture, which I wasn’t bad for a custom diesel tank.

New custom made aluminium tank!

To protect the tank I glued on some plastic slats to the bottom, figured they would help with all the bumping around. I then bolted it into place with the L fittings I had them weld on.

Installing the fuel fill nozzle.

Next I installed a new diesel fuel fill nozzle on deck.

Connecting the hoses

Then connected new hoses for the fuel intake and the vent. I reused the vent from the holding tank which was the same fitting the existing diesel tank used.

The new tank installed!

The last step was putting a T-junction and a tap on the engine diesel lines that allowed me to select between either tank. This was made easy with the primary diesel tank being so close.

The final final step involved filling the second tank and checking for leaks. I bled the lines and ran the engine on the secondary tank for a few days. Worked really well! All in all the total cost was under $1000, so well worth doing.

On the big trip I carried two diesel jerry cans on deck to give me a total capacity of 62 gallons and a range of 400 miles. That really came in handy on the pacific crossing where I had to motor for nearly 300 miles in the doldrums!

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Author: Chet

Avid sailor.

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