Water in Diesel

[Reighnman]

Thankfully my fuel/water separator has done it's job but has anyone experienced water in the diesel and any likely areas of intrusion? I disconnected the fuel line and did a rain test on the fuel cap and it was dry but already ordered a three pack of replacement rings. The exhaust vent seems fine and the loop is in the hose. The top of the tank is pretty dry so can't really see it being the fuel gauge sending unit but guess it's on the list. I did top the tank off last fall and added Bio Kleen fuel biocide and also Clear Diesel. Could I have added too much? Will call the manufacturer tomorrow.

My plan is to pump the tank out into a couple of jerry cans and take to the county hazard waste disposal. The amount of water was enough to almost fill the water separator each time I ran the engine for 20mins.

[moonlight]

The separator is doing it's job.
But that is no indication of the amount of good clean fuel you're about to throw out.
Rarely do the additives emulsify the water.
The water is usually free water on the bottom of the tank.
Your pickup tube sits 1/4-3/4" off the bottom.
Pull the pickup tube, insert a piece of copper tubing to the very bottom, and if you're both handy and lucky the pickup tube is in a corner of the tank.  Now you need a way to tilt the boat in that direction.  Two or three 250# buddies huddled around a case of beer is enough.  DO NOT TRY TO USE SIX 100# BIKINI BABES AND WINE FOR THE SAME TILT.  THEY TEND TO FIGHT WHEN HUDDLED LIKE THAT.

Now, pump the pure water out from the low corner through the copper tube (which you've angled to the corner; remember,  you can even gently bend it to point thataway).

You may get a quart. Maybe two, but that'd be rare.  Then you'll see you're pumping pretty diesel fuel; greenish if street legal, red if off-road (dyed to indicate it's higher sulfur content)

Change your water separating filter (it caught other crud you can't see), and put it all back together.

The water is condensation.
The tank breathes, just like you, but slower.  But every day it gets warm, expands, exhales through the vent.  Every evening it cools, inhales, humid air.  Over time the humidity in the tank airspace reaches enough and some falls out straight through the fuel to sit on the bottom.

You minimize this by reducing the vapor space, making for more shallow breathing. You do that by keeping the tank FULL.  But really, unless you use the boat daily or weekly, your tank is already too big.  Get a 3-gallon portable tank it'll run all day at least.  More likely, all year.  And periodically you carry that off the boat and give it to anyone with a diesel truck or tractor.  They burn it, you buy new... problem solved.  Before a long cruise, hook the big tank up again.

[Reighnman]

Thanks for the tips! The Admiral would burn the boat down if I had 6 100lb bikini clad females on it! I did try siphoning the water with a copper tube on the bottom of the tank but only got fuel. The listing of the boat/tank and pulling from the low corner makes sense. I was also reconsidering tossing all the fuel and perhaps siphoning the first 7-9 gals from the top, then lower the copper tube to the bottom to remove the last couple gallons. I'll try your suggestion first though.  The idea of the smaller tank makes sense too. Even my longest motor of 60 miles barely dented the gauge.

I'm also having trouble removing the small fuel filter on the motor. That aluminum ring won't budge.  The 25 is a great boat, but I keep having CP27 engine room envy every time I'm down there.  Next project after this one is the water pump impeller. Not a fan of having to remove the oil filter to access the impeller.   Oh well, one issue at a time. Thanks again for the help!

[captronr]

We had friends with a 30ft boat that had a diesel with large internal tank.  He fought that every spring with water/mold/gunk in his tank.  He never got on top of it.  I urged him to take the tank out, get it cleaned, and NEVER use it again, but instead get a 3-5 gallon portable tank.  Use it 3 months, then as another stated, give it to a truck/tractor owner and buy new.

I have a Kubota diesel tractor and have not had any issues with it, but it's tank is only 5 gallons and it is stored inside, and not exposed to moisture like in a boat.

Ron

[TopsailB]

 Gasoila paste (https://www.gasoila.com/products/gauging-paste/regular-water-finding-paste.html) is my go-to to determine the presence of water and how deep it is in the bottom of the tank. Preferably on a dip stick or alternatively a drain snake to insert through the fill to the bottom of the tank. Apply a small stripe several inches on the stick/snake and it turns from yellow to red to indicate water/depth. Once I know the scope of the problem it's easier to determine the best course of action. I typically check for water prior to any trip or filling the tank.

[moonlight]

It's also worthy of consideration; maybe your filter really did already do it's job completely!

Where you thought you had water in the tank, it's already all been extracted and placed in the filter.

So, change the Racor, and keep going for a good season.

I had  a Boston Whaler 17' Montauk in the  shop for refit last winter.  It came equipped with a 30 gallon tank.  It left with two 6 gallon tanks strapped in the same spot.  He kept the boat on a hoist/lift at the country club, so was forced to tote fuel or buy on the river @ +$1.25/gallon.  And there's no way his Mercury 90 2-stroke would burn 30 gallons in a weekend tubing.

We also deleted the Mercury oil-injection.  Those early systems had a peculiar method of notifying you that the oil pump had failed, but putting a piston through the side of the block.  No alarm or other indication until catastrophe. 

So mix the fuel:oil, in a tank he can tote in the back of his pickup truck, and with drybreak fittings can swap from one tank to the other quickly.

He then got transferred to DC, so that boat is back in the yard with a FOR SALE sign on it.  $15,000 OBO if anyone's in the market and near Mandeville, LA.