Cleaning Inaccessible Fuel Tank

[nigheandonn]

My friend's boat has a large 40 gallon plastic petrol tank. The deck ope is not large enough to facilitate removal of the tank. There is no suitable inspection ope and the only means of inspection is to remove the sender probe, leaving a 40mm ope. He has had a few attempts at cleaning it, prompted by recurring fuel problems since he bought the boat last year. He has drained the fuel from the tank - he showd me a pic of the fuel after he had allowed it to settle there was a fair deal of crud in the bottom of the glass container. But he is unsure if he has removed the crud entirely :- with baffles in the tank he thinks flow could be considerably restricted -and with the setup as described he can not just give the tank a good shake or inversion or onspection..
He is now seriously considering cutting up the tank (please no H&S advice) and removing same and replacing with a smaller removable tank which could be shaken about and cleaned much more easily. This seems so drastic that I thought I would ask if anyone had dealt successfully with this problem by clever ways of cleaning the tank.

Thanks in anticipation of your help.
Tony

[klem]

I would suggest having him try to find someone who does fuel polishing. Basically, they circulate the fuel from the tank through a set of filters and back into the tank for a while. They do it with enough flow rate to agitate stuff in the tank.

[nigheandonn]

Originally Posted by klem

I would suggest having him try to find someone who does fuel polishing. Basically, they circulate the fuel from the tank through a set of filters and back into the tank for a while. They do it with enough flow rate to agitate stuff in the tank.

He mentioned that fuel polishing was not an option with petrol as opposed to diesel ie the guy who polished fuel locally would have obliged gad it been a diesel tank but was apprehensive of polishing petrol. Don't know anything about it myself. Is that a reasonable point?

[Chief Engineer]

I don't know of anyone who polishes gasoline tanks......way too dangerous...over here. proper/legal disposal of contaminated gasoline is very expensive.

[nigheandonn]

The tank is about 4 foot long and most likely baffled. My mate thought that the presence of baffles was preventing the crud from flowing to the ope at the rear of the tank where he was able to suction off fuel. Apart from tilting as much as possible in a fore and aft direction of trying the compressed air bubbling technique mentioned, are there any other suggestions as to how to overcome this?

Thanks again!

[DeepFrz]

of trying the compressed air bubbling technique mentioned

WHAT? Where in the world was that mentioned?

You are messing with a very volatile fuel. My suggestion is to hire a professional who knows how to handle gasoline fuel tanks.

[Chief Engineer]

How about a picture?

[klem]

Originally Posted by nigheandonn

He mentioned that fuel polishing was not an option with petrol as opposed to diesel ie the guy who polished fuel locally would have obliged gad it been a diesel tank but was apprehensive of polishing petrol. Don't know anything about it myself. Is that a reasonable point?

Sorry, I didn't read your first post very well and assumed diesel. I don't know of anyone willing to polish a gas tank either. You would need a way to displace all of the oxygen in the air while doing it. I am sure that some backyard mechanic does it, just like the guys who will weld on a gas tank with the engine running and the exhaust plumbed back into the tank.

I know of people flushing with other fluids if there is a drain at the very bottom of the tank. You do end up with some disposal problems in the end though.

[ViribusUnitis]

How about just getting someone with proper skills to install an inspection hatch. In the process you'll have to drain the tank.

Then after the hatch is installed, have it cleaned with a pressure washer. Drain it, dry it, and put it all back together. He'll need to make doubly sure that it's dry before he refills it, but it should be completely doable.

[nigheandonn]

Originally Posted by ViribusUnitis

How about just getting someone with proper skills to install an inspection hatch. In the process you'll have to drain the tank.

Then after the hatch is installed, have it cleaned with a pressure washer. Drain it, dry it, and put it all back together. He'll need to make doubly sure that it's dry before he refills it, but it should be completely doable.

I just wonder if the installation of an inspection hatch is an option? All of the new tanks for petrol I note in catalogues show no access hatch - presumably because the fuel is so volatile?

T

[nigheandonn]

Originally Posted by Chief Engineer

How about a picture?

I'm sorry I do not hace a picture to post.
I haven't actually seen the tank myself it being on my friends boat -He referred me to this type of tank as being similar to his own.

Moeller 31-90 Gal OEM Permanent Fuel Tanks - iboats.com

[ViribusUnitis]

Originally Posted by nigheandonn

I just wonder if the installation of an inspection hatch is an option? All of the new tanks for petrol I note in catalogues show no access hatch - presumably because the fuel is so volatile?

T

I dought that. Amost all automobile tanks include inspection hatchs of some sort. Often they are what the "in-tank" fuel pump is installed in.

Properly sealed, I can't immagion an inspection hatch being worse than a dipstick, or anything else.

[Boracay]

How difficult, expensive, time consuming and messy is it to pull out the tank and replace it?

Work out what needs to be done, line up everything needed and just do the deed.

All the other solutions look like fiddling round the edges with a potentially dangerous bit of equipment and it still might not function correctly.

By the time the petrol was managed in an appropriate manner (if this can be done at all) it might come out quicker and cheaper to just replace the tank. Filler, fuel and breather lines and filters could be replaced at the same time.

Maybe even have a think about how all that gunk got into the tank in the first place.

[s/v Jedi]

It's already drained. Pressure wash it with fresh water using both deck-fill and sensor openings. Drain into bucket(s) and use oil absorbent cloths to clean the surface; catch any crud and discard that properly.

All petrol/gas should be gone after that and I would use air (even hot air) to vent the tank dry (into deck fill opening and out the sensor opening.

cheers,
Nick.