Adding a permanent fuel tank in a 1992 Sea Nymph 161Fishing Machine

[S Gilbert]

I will redoing the inside of my boat this winter and would love to install a fuel tank below the aluminum floor and looking for tips and advice. Thanks

 

[airshot]

Dimensions are needed to find a tank that will fit. On my Sylvan 16' the tank sits under the floor about 2/3 of the way back. Two long aluminum stringers run back toward front with tank in between. A 3/8" plywood deck covered in carpet covers the tank. On mine the fill outlet comes up inside the splash well...very awkward to fill the tank with two out boards in the way. Often thought about moving it ! My tank is 18 gallons and my 40 up Merc can run a looking time on that much fuel. No tank to trip over or be in the way and mounted at a perfect balance point. Lots of different size and shaped tanks out there, time to do some searching, you won't be sorry.

 

[S Gilbert]

Thanks and everything you said is why I’m thinking about taking this on.

 

[crazyeddie]

Check out Moeller poly tanks sold through Ocean Link Inc. They offer a ton of different sizes, capacities, shapes, fillers, pickup tube locations, and with/without sending units for gauges and they have the blueprints for every tank on their website.

Find one that suits your space constraints and fabricate a tray out of angle aluminum and straps out of aluminum flat stock to hold it and secure it to the hull. The hardest part is deciding where/how to mount a filler neck and fuel cap as 2" marine fuel filler hose is thick, heavy, and not easy to bend in a tight radius. The tank you select needs to be mounted with pickup tube end of the tank facing the transom so that it doesn't suck air should your tank be near empty and the hull in a bow-high attitude. You'll also need a tank breather that mounts through the hull well above the water line to vent fumes away from the hull. The breather hose needs to be marine fuel-rated breather hose (most are 5/8") and you need adequate space to route the hose up from the vent fitting, shaping it into an upside-down p-trap, before running it down to the tank as a means of blocking water from entering the tank through the breather hose should you get slapped around on the water.

I spent more time in my boat with a tape measure, looking at blueprints on my laptop and visualizing what would work and what wouldn't, than I spent actually installing the tank. Plan carefully though, most tanks are made to order and cost about $50 to ship so you don't want to send it back!