Why you should inspect your fuel tank every now and again...

[alt]

[quote name='alt' timestamp='1297118277' post='55669']
Friend rang me to say engine died on him, suspect was water in the fuel tank. The tank in question is an in-built stainless steel tank for a petrol RIB.

After checking the lines we confirmed there was a LOT of water in the lines/fuel filter/fuel pump/injector rail.

Once all that was cleared out, it was time to drain the tank. This is a 500 ml sample of what we took out. Those of you who are squeamish might want to look away now :o


[/quote]

My own boat is a diesel with a s/s tank, and this is the exact reason I keep it full all the time! The water ingress in this situation was purely from condensation as in fairness to the owner, they're very careful with regards to fuel transfer/clean jerrycans etc...

Just goes to show! This could have let the owner down at the worst possible time, thankfully this time it was on the pontoon!

[BogMonster]

Did he have a water separator fitted? I'm not clear what happens when they totally overflow with too much water - does it block the flow to protect the engine, or let it through?

What's a sensible period to syphon the tank from the lowest point - annually? So far I have only tended to fill up every 3rd/4th outing as the 150L tank lasts for ages, the Osprey tank is GRP which hopefully is a bit less susceptible than SS but still something I wonder about. I syphoned the Humber tank a couple of times in the 4yrs I had it and it was pretty clean (plastic tank under the seat but usually filled after use).

I've seen stuff like that on big commercial generators, in fact I've got a bottle of diesel at work somewhere that if it's below about 10 C you can turn it upside down with the lid off and the contents won't move...

[alt]

There was no water/fuel seperator, however I have advised that this should be his next purchase... which I assume will be! Very easy to fit too.

However, this filter still wouldn't have stopped that build-up on the tank.

As for tank cleaning... it depends really. Take for example on my diesel sports cruiser....
Truck arrives and fills my 1000l bowser. First filter here is a basic strainer to remove any large dirt particles.
I then fill the boat from the bowser. On the bowser is a water/fuel seperator (I forget what micron filter)

Then in the boat is another water/fuel seperator and finally the engine fuel filter.

In this case, I have never cleaned out the boat fuel tank, but the bowser gets cleaned out at the start of every season (or any time there's less than 10 litres in it actually)

[willk]

Hi alt

Nasty. Not very surprising though - I'd bet most boat fuel tanks are similar, it's just that the filter/separators do their job. I've had terrible problems with diesel at work, so much so that I've had to have a 10,000L tank commercially cleaned (£££££!). Most of the crap was from a particular supplier but the water is a general condensation issue.

Slightly OT, but kinda relevant: I've often been warned "Don't let the tank in the RIB run low, 'cos you'll suck up all the crap from the bottom"

I don't see how this can be true?

A. Water sinks, so it's gonna be at the bottom.
b. A RIB tank is a big cocktail shaker when at sea - so any other crap will be "homogenised".

Any thoughts?

[Erin]

I suppose the only argument in favour of not letting the tank run low, is that if you do then the homogenised crap will be very concentrated homogenised crap, possibly lacking enough petrol to run your motor. At least with a full tank the crap is diluted and hopefully not enough will get filtered out to block the filter or stall your engine. I'd rather suck 10 litres of dilute crud through my filter than 10 litres of concentrated crud.

Whilst water in fuel is not good, it's obviously much worse in diesel due to the risk of microbial growth. I have sometimes gathered a teaspoon of water from my portable tank at the end of a season, but the amount of water in that coke bottle seems a hell of a lot just for condensation. Strikes me as though there was some dodgy fuel involved, or a large open breather sucking in lots of air on a foggy day!

[willk]

Originally Posted by Erin

or a large open breather sucking in lots of air on a foggy day!

He's from Galway, the Wettest County in Ireland
They get rain on 230 days each year!

More seriously, don't underestimate the potential for water accumulation via condensation. I have a cooling water tank at work that is about RIB tank size. It has a loose lid and I have to remove about 10-15 litres of water from it every four or five months...

[willk]

Originally Posted by Erin

I suppose the only argument in favour of not letting the tank run low, is that if you do then the homogenised crap will be very concentrated homogenised crap

I understand this, but if you continue the logic, surely by the time you have burned off 4/5ths of a tank of dilute crap, your tank is 4/5ths cleaner and the next time.....

[biffer]

i use fuel set additive in my old girl and have a racor filter, yamaha do a good filter that has an orange ring in the glass bowl, it doesn't float in fuel but does in water, it's a good filter and not to pricey as racor and separ are

[Erin]

Originally Posted by willk

I have a cooling water tank at work that is about RIB tank size. It has a loose lid and I have to remove about 10-15 litres of water from it every four or five months...

I assume your 'cooling' tank is at below ambient temperatures. This will naturally attract more condensation won't it? Anyway, I've always understood massage parlours are prone to high humidity

[BogMonster]

Originally Posted by alt

There was no water/fuel seperator, however I have advised that this should be his next purchase... which I assume will be! Very easy to fit too.

However, this filter still wouldn't have stopped that build-up on the tank.

As for tank cleaning... it depends really. Take for example on my diesel sports cruiser....
Truck arrives and fills my 1000l bowser. First filter here is a basic strainer to remove any large dirt particles.
I then fill the boat from the bowser. On the bowser is a water/fuel seperator (I forget what micron filter)

Then in the boat is another water/fuel seperator and finally the engine fuel filter.

In this case, I have never cleaned out the boat fuel tank, but the bowser gets cleaned out at the start of every season (or any time there's less than 10 litres in it actually)

No I realise that but the point being I'd rather grind to a halt with a water separator that said "enough" than grind to a halt with an engine full of water ... same practical result (lack of propulsion) but assuming you make it out alive and with the boat in one piece, it should be a whole lot easier and cheaper to fix.

I only fill my RIB out of the pump at the service station and I believe they are fairly well filtered (never had any problems with crappy fuel in the Humber anyway) but I wonder whether the fuel tank breather is likely to let water in when you are out in rough conditions - it seems to get everywhere else.

A separator with a glass bowl is a good thing and something on my "to do list" (which probably means it won't ever get done but....)