Pontoon Boat & Deck Boat Forum

Our 2016 Premier with a 115 Yamaha is getting water in the fuel tank. It has Sea Legs and sometimes when it is loaded we get water flowing over the tank, that is in the transom. There is four penetrations in the top of the tank. Three, the fuel filler, fuel gauge unit,and inspection cover have multiple screws around the perimeter and a rubber gasket. I took these apart and applied a gasket maker/sealant to these. The fourth, the fuel supply fitting bulkhead has no visible gasket and I don't know how it is suppose to go together. I did not take the nut off, as I don't know if it may fall apart in the tank, so I just piled the sealant around this fitting.
What is the most likely cause of water getting into the tank? How are the fuel supply fittings put together?

The worst problems I ever had with water in the fuel was caused by water in the storage tanks where I bought the gas.

Rick's point is a valid one. Are you sure the water is leaking in and not coming from your fuel source? It certainly sounds like you've done everything possible on your end to seal the penetrations.

Of course water could come from the gas source. But I believe that is less likely because I only got it from gas stations, no dock gas or gas cans. Also the fuel intake fitting looks suspicious, but I don't know how it should look.

bkvanbek wrote: ↑

Thu Jul 29, 2021 5:27 am

Of course water could come from the gas source. But I believe that is less likely because I only got it from gas stations, no dock gas or gas cans. Also the fuel intake fitting looks suspicious, but I don't know how it should look.

The worst fuel/water problem I ever had (actually the only one) came from a local gas station; from their pump right into my boat tank.

I am curious how you know the water came from a gas station. But really what I am trying to find out is how the fuel fitting, at the tank, for the line to the engine is suppose to be waterproofed.

Bulkhead fitting should have a nylon washer top and bottom. I did a fuel return on an old car tank like that when installing fuel injection. It's below the fuel level on the side of the tank and never leaked. It had a shoulder on it and only used a nut on the bottom though. If they used a fitting with no shoulder and a nut then the threads are a leak path even if it had a rubber or other sealing washer under the nut. If there's nothing under the nut it's even worse.
https://flic.kr/p/aqJpQY

bkvanbek wrote: ↑

Sat Jul 31, 2021 6:01 am

I am curious how you know the water came from a gas station. But really what I am trying to find out is how the fuel fitting, at the tank, for the line to the engine is suppose to be waterproofed.

Well; there were a few clues.

1. The new boat ran fine before I gassed up there; but was messed up after. I believe that about seven gallons of water were ultimately removed from the boat tank; which is a good bit more than one would ever get from condensation.
2. Right after I bought the gas; they closed it down, and had some multi-point pumps running throughout the property for several weeks attempting to alleviate the groundwater contamination from the old leaking tanks.

I’ll hazard a guess that, when the seasonal groundwater table was high; water got into the tanks. During the dry season, when the potentiometric surface of the groundwater was low; the gasoline leaked out of the tanks into the surrounding soils, and had been doing so for many years.