water in starboard tank


L

lakecabin36

New member
I have a 1990 Formula 36PC (not express) with twin Mercruiser 7.4 liter Bluewater Inboards. Our first summer was last year and we battled water and debris in the starboard fuel tank most of the summer and went through about 5 fuel/water separator filters. We had very little problem towards the end of the year. The boat is stored inside heated (we are in South Haven, Michigan). We got the boat in early this year, end of April, and are having more water in the starboard tank again. I put another new o-ring on the fuel cap a couple weeks ago, and when I loosened the cap this morning, I noticed a vacuum sound (weather had cooled quite a bit), which makes me wonder about the fuel vents. There are three on the side. Anyone know anything about the fuel vents?
 
I get to reply to myself, but if anyone has similar issues, maybe this will help. I said I have 3 vents on each side; 2 are fuel tank vents, the third is water and septic. I took the old vents off (not an easy task on this boat) and the starboard tank vents were plugged. I cleaned the screens and put new gaskets on and re-installed them. It seems that with the weather changes so much this spring (warm, cool), the clogged vents created quite the vacuum in the fuel tank and it was literally sucking water in through the gasket on the cap (our fuel fills are fairly flush with the non-skid surface). At least that's my theory. We will see.
 
O ring on the fuel fill is usually the culprit. Replace the o ring every 5 years and lubricate it with a silicone grease to keep it in good shape.
 
Gary is right O rings for sure. Formula has diverters that can be mounted. Directs the water away from the fuel cap.
 
Thank you all for your input. Appears the problem was a combination of bad o-ring, clogged fuel vent screens, and previous owner put fuel with ethanol in starboard tank. I had the starboard carburetor rebuilt and the mechanic said it was obvious ethanol fuel problems.
 
We just picked up a 2000 400ss and have two really bad tanks of very old fuel. The sample from the fuel filter looks like balsamic vinegar salad dressing with 50/50 water gas. Oh, and they are almost full (125 each).

We were able to have one tank polished and removed about 5 gallons of crap out of one tank. Water, granular something and general sludge. The fuel in that tank looks brand new now.

They ran out of time on the other tank and should be here this week to finish up.

I hope this will solve our issues.

I will keep everyone posted as to the success or failure. And the cost. So far, I estimate Hal’s the cost and hustle of pumping out the tank. This process also vacuums around any baffles as well.




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I wish we had the option of non ethanol gas here in CA. And since I am in a marina on the water, I don't have any other options. Every fill up, I add a bottle of the Mercury Quickare Fuel Additive (#1) to keep the ethanol suspended in the fuel. And it's cheaper to buy it at the local Walmart than go to West Marine.
Good luck on solving your fuel issue.
 
I did not know that gasoline could be polished. I was lead to believe only diesel could.
 
Yes. Gas can be polished as well. Takes specialized equipment. However, it does not boost the octane in bad fuel. Additives can.

However. Never run hard with bad gas. You can kill your engine.


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