water in fuel

Question to the forum:
I have a new boat that I bought in April with twin Yamaha 300’s. Have only put in fuel at one marina. These are the facts:
Tank holds 230 gallons, and last week put 110 gallons in at the marina to fill tanks for offshore trip. Immediately after fueling started offshore and about 10 miles out my port engine alarmed that there was water in the fuel, so shut it down and returned home on starboard engine, and on the way called marina to tell them of the problem.
When I got in stopped at the marina and they said no one else had reported a problem. 2 days later had service manager from the dealer where I bought the boat find the filter was full of water and also water in the in engine separator, said it must have come from the marina.
Called the marina manager and was told no other problems reported and the water in the fuel was not from them and unwilling to pay for the repair.
What do you folks think?

Sounds like you had water in the tank from sitting (also could have come from the initial fill). Run the boat, pull the filter, dump it and look for water. When you dont see water, after a filter pull, put a new filter on and have a great run. Always keep your tank full to prevent condensation. If you have alot of water you may have to pump the tank.

A 230 gallon tank can collect 8oz (all it takes to clog a filter) in no time. Ethanol fuel is like a magnet for water. Good luck!

-Albemarle 248xf “Chella”
-Dolphin 18BC Pro
-Miscellaneous boats

Edit - I say sitting because you purchased the boat in april and have burned only 110 gallons without refilling. The air space in your tank through the hot months could easily collect water.

Are they HPDI’s or 4 strokes?

They are 4 strokes. Also, have been running the boat all summer and fall, multiple fill-ups.
Thanks for the input

Empty the fuel/water separator, empty the fuel filter cup mounted on the engine. Fill with fresh gas and run the boat. The starboard engine didn’t shut down. Being 10 miles off, you should have alarmed on both motors if you had that much water in the tank.

how long was the boat sitting with a half tank of fuel?


Would not take long for condensation to build up with some of the big temp swings we get this time of year. Another thought to consider is the large amounts of rain we have been getting. Is there a possibility rain water has gotten into the tank? Fuel sending units will start to corrode and loose their seal against the top of the tank. Once this occurs easy for water to infiltrate the fuel tank.

One more unmentioned consideration is the location and orientation of the tank vent. If it’s installed too low, or not oriented correctly it could take in water while running in a sea. Just a thought. Give it a look.

Capt. Larry Teuton
Swamp Worshiper

A friend had so much water problems he was ready to sell his boat. I spent about an hour just sitting and looking at the whole fuel system. The tank vent was incorporated into the fill line with a cap that didn’t close air tight. A very hard rain would cause enough water to puddle up under this screwy cap and inter the tank. We removed the fill cap and replaced it with standard O ring sealed cap and installed a standard overboard tank vent, pumped out the tank and refilled with new non alcohol fuel. Over a year ago and no more water problems.

Hope this helps.


I had that issue after filling up in Bimini this summer with my F250. I pulled the fuel/water separator and it looked bad when I poured it in a glass. I replaced it and the fuel filter and it’s been fine ever since. Not sure if it was bad gas from the marina in Bimini or all the bouncing on the ride across the stream. Ran fine until boat settled into the no wake in Ft. Lauderdale, that’s why I say that.

Seah Hunt Ultra 234 Yamaha F250
Sea Pro 190CC Yamaha F150 (sold)