Quick Tech: Mounting & Plumbing An Accessory Fuel Tank


The idea came about from our riding group doing extended day rides. The long distances required us to find fuel wherever we could. This was even more difficult when riding in protected areas where fuel spillage becomes an issue. This system is very simple and it works without the use of pumps, instead working solely on the vacuum created in the main tank vent hose. The main fuel tank draws from the auxiliary tank first. This way also cuts out any chance of fuel spillages while transferring fuel from jerry cans being carried on the back.

This walk-through is the first one I made using an older style fuel cell fitted to the swim platform of my own Kawasaki Ultra 300X, I have since made others using a newer style tank, and many others here in Australia have since copied the idea (with my permission) to their own skis. Many have had no mechanical knowledge and have found it very simple to replicate.

Below are the steps necessary to replicate this very easy-to-install auxiliary fuel tank to your runabout. It shouldn’t matter if it’s supercharged or not, the fuel delivery system remains the same.


You’ll need an insulated and self-contained fuel cell, two sets of hose quick connects (more can be used if you want to remove the hose completely from the rear tank), fuel hose (6mm), ratchet-style tie downs, zip ties, hose clamps and fittings for the fuel cell.


First, locate and remove your vent hose from your ski’s fuel tank. Add a length of fuel hose to the fuel tank vent nipple, on the other end of this hose you place a 6mm fuel-rated quick connect. Place the opposing quick connect on your OEM vent hose, this allows your OEM fuel tank to operate as it was designed (noting the non-return valve has not been removed).

[Above: Next, fit the fuel cell to the rear of the ski. The tank most commonly used holds 45 liters. On any of the Kawasaki’s this is easy because the rear deck is flat, on other branded skis heavy foam packers can be glued to beneath the tank to level it out. I have made a custom ratchet webbing strap to firmly hold the fuel cell in any rough conditions.]

[Above: Next is to connect the 6mm fuel rated hose to the rear tank pick up and another to the vented fuel tank cap. Find or make an entry point in the rear of the ski, once again Kawasaki have made this easy with the rear vents being utilized. Others have drilled holes and used grommets when not in use.]


The fuel lines are then tied away from the engine and threaded forward to wear we made the quick connect connection on the OEM tank. Loose hanging zip ties can be seen in my pictures along with where I threaded the OEM breather through the upside down sensor bracket.


Then disconnect the OEM breather quick connect and locate the hose going to the OEM tank nipple and the pick up line from the rear accessory tank, cut this to length and fit an opposing quick connect, connect these together, then locate the OEM breather hose and do the same with the breather hose coming from the fuel tank, measuring cutting and fitting another opposing quick connect. (This procedure only has to be done once as from now on it can only be fitted up one way.) The idea of the quick connects is the tank can be removed at any time and the ski returned to OEM. All within approximately 2 minutes. The quick connects are also self sealing so no spillage in your hull.

[Above: You then fill your OEM tank on the 300X (this is 82 liters to the filler neck), fill the accessory tank (of which, is 45 liters). This gives a total capacity of 127 liters. As you ride your ski the vacuum created in the OEM tank draws the fuel from the rear tank utilizing your unchanged OEM vent line with the non return valve still in place. Once the rear tank is empty the system is no different to OEM the air is now being pulled in the vent line via the rear tank.]

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