Filling gas tank issue

I know this has been discussed but I cant find a solution to the problem. Manual says 39 gallon tank and the most I can get in is 30 gallons according to the fuel gauge which will read 3/4 full. I pump the fuel slowly and see and feel the fumes coming out of the vent beside the fuel port. The back pressure in the system builds up and the pump shuts off. I cant even feather the fuel into the tank. I called Moomba and they said that even though it says 39 gallons, 34 is the max. Regardless the max, I can still only get 3/4 to read on the gauge. Any suggestions?

Mine will say 85-93% on the trailer then go to full when it’s on the water. Does yours change when it’s on the water (not moving)?


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i was able to get my gauge to read 98% by using jerry cans and filling it that way at the dock.

It shows 3/4 on trailer and in the water (not moving). Its sits at about the same attitude. I know the gauge works off a float in the tank. I think it just builds up too much back pressure before the tank fills. Talked to a dealer and they said pump really slowly to avoid back pressure. I thought I was pumping slow but maybe I'll try and pump really slow next time. I just want a full tank for extra weight and not going to gas station every other time out.

I may also try the jerry cans as well.

I'll trade you the new boat issue vs. the old boat issue of reading empty after only burning 25 gallons (out of 40)

When I know my boat will take 2 - 5 gallon jerry cans to fill it (approx. ¾ full), I put one in then I have to wait a few hours or overnight until I can put the second can in and only then it will take the second can.... PITA....

I use a Tera battery operated transfer pump with auto stop to transfer the gas as it eliminates the mess if the back pressure won't allow the fuel in the tank.

https://www.amazon.ca/TeraPump-TRFA0...ateway&sr=8-13

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Originally Posted by justflyinglow

I know this has been discussed but I cant find a solution to the problem. Manual says 39 gallon tank and the most I can get in is 30 gallons according to the fuel gauge which will read 3/4 full. I pump the fuel slowly and see and feel the fumes coming out of the vent beside the fuel port. The back pressure in the system builds up and the pump shuts off. I cant even feather the fuel into the tank. I called Moomba and they said that even though it says 39 gallons, 34 is the max. Regardless the max, I can still only get 3/4 to read on the gauge. Any suggestions?

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I have the exact same problem and I'm convinced that it's a venting issue. My dealer has replaced the one-way check valve directly above the tank and it didn't help. Like most fuel tanks, the tank vents through a charcoal canister and I wonder if it's inadequately sized.