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Old 14-10-2011, 13:50   #16
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Re: How Far Off the Tank Bottom Is a Fuel Pickup Tube ?

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Originally Posted by James S View Post
I'm not saying they don't exist...just that I've not seen em.
Look...they are DEFINITELY out there and not a problem (not anymore than other types of fuel leaks)
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Old 14-10-2011, 16:04   #17
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Re: How Far Off the Tank Bottom Is a Fuel Pickup Tube ?

On a brand new boat or new tank, why would you not want a bottom hose? It seems like that would prevent impurities from collecting in the take by forcing them to go out in small doses immediately. it would also keep the fuel from getting too old(probably not a serious problem since the tank gets bounced around enough to continue mixing the fuel).
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Old 14-10-2011, 16:13   #18
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Re: How Far Off the Tank Bottom Is a Fuel Pickup Tube ?

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Originally Posted by davefromoregon View Post
On a brand new boat or new tank, why would you not want a bottom hose? It seems like that would prevent impurities from collecting in the take by forcing them to go out in small doses immediately. it would also keep the fuel from getting too old(probably not a serious problem since the tank gets bounced around enough to continue mixing the fuel).
Exaggly...plus many other conveniences...like the ENTIRE fuel systen that is hoses prone to chafe and connections/valves that can leak...you just have to keep an eye on the fittings....but i love my sight gauges as they are accurate and show me the color of the fuel in the tank before it get to the RACOR.
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Old 14-10-2011, 16:15   #19
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Re: How Far Off the Tank Bottom Is a Fuel Pickup Tube ?

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Originally Posted by davefromoregon View Post
On a brand new boat or new tank, why would you not want a bottom hose? It seems like that would prevent impurities from collecting in the take by forcing them to go out in small doses immediately. it would also keep the fuel from getting too old(probably not a serious problem since the tank gets bounced around enough to continue mixing the fuel).
I'd guess that condensation on the walls of the tank could lead to vegetation that could clog a bottom feed. It can happen when you don't feed from the bottom.
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Old 14-10-2011, 16:56   #20
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Re: How Far Off the Tank Bottom Is a Fuel Pickup Tube ?

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Originally Posted by hummingway View Post
I'd guess that condensation on the walls of the tank could lead to vegetation that could clog a bottom feed. It can happen when you don't feed from the bottom.
Yes and a bottom feed is easy to clean and drain crap quickly..one of those nice features I was talking about...but as it was said...constantly pulling from the bottom tends to filter out smaller amounts of goo before they take over ALL those unusable gallons in a top feed.
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Old 14-10-2011, 17:01   #21
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Re: How Far Off the Tank Bottom Is a Fuel Pickup Tube ?

On model aircraft the fuel feed line was always entered the top of the tank to a normally low point. A precaution against fuel running from the pipe after a crash, or inverted flying. On a boat that's being bounced about it is a problem if the tank contents are low and the bottom is fairly flat. Easy to fit the tank to one side of the keel with a definite low point, if that's no possible then baffle plates angled towards the pickup point will help.
Parafin heaters used to have three perspex rods in the tank. Any of them in the fuel looked black, those dry at the end were clearly a different colour and reflecting daylight. This should work for diesel too.
A coarse filter on the inlet will trap coins, bolts etc. A fine mesh on the suction pipe will trap sand, there should be a dust filter on the engine line to protect the engine, and a water trap for condensation in the diesel.
A proprietry 'diesel cleaner' additive will remove or negate any microbiological activity if the boat has been laid up for a few months.
If you get a chance to lift the tank then get to a welding shop to include some/all of these mods. Standard tanks rarely have them, RNLI and others, are kept busy by 'engine related issues' including "I THOUGH WE HAD ENOUGH FUEL" and "IT JUST STOPPED AND WOULDN'T RE-START". In spite of their best efforts they don't get to all of them in time.
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Old 15-10-2011, 05:29   #22
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Re: How Far Off the Tank Bottom Is a Fuel Pickup Tube ?

since the bottom feed has definite advantages as in cleaning the tank bottom, then why not have the pickup tube come in the top and go right next to the bottom?

Also, I dont like screens on pickup tubes, I think the filtering system should be designed to handle that and wonder if my monel Seafarer (Seafair, Seafare , not sure) tanks have them. They are top feed.

I tried to remove the fitting, it looks robust and looks like brass or bronze but It did not want to move and I worried if I really tried it might shear off?
Has that ever happened to any of you?

I know If the tank was out of the boat, I would have no trouble working on it.
I know my tank pickup is off the bottom cause when I clean them using a vacuum jar with a pickup tube right on the bottom I get dirt which I dont get from the builtin pickup tube.

I was thinking of setting up a pump to pull off the bottom directly, run thru a filter and then have it go back into the tank to help clean it. Do people do that and how long would you run the pump? If you drop a copper tube down the fill fitting, where would you put the return fuel?

Right now I could pump from one tank to the other and not overflow, so I could just do that over and over. What do you think? These tanks have a fill fitting, a pickup and a vent and no return line.
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Old 15-10-2011, 06:32   #23
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Re: How Far Off the Tank Bottom Is a Fuel Pickup Tube ?

Any of you folks with mesh screens on your pickup tubes I would recommend you remove them before you have trouble. You want the primary filter to take out the junk, not some very difficult to get at, easy to forget piece of mesh down near the bottom of your tank.
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Old 15-10-2011, 08:17   #24
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Re: How Far Off the Tank Bottom Is a Fuel Pickup Tube ?

On my 38gal diesel fuel tank, the fuel pickup is cut square and some inches off the bottom.

On the mesh screen covering the pickup hose end:
I was having fuel starvation problems that was caused by the mesh screen at the end of the pickup tube getting clogged over time. Local boaters make it a policy to remove these screens for this exact reason, relying on the Racor to do that job.
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Old 19-10-2011, 07:52   #25
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Re: How Far Off the Tank Bottom Is a Fuel Pickup Tube ?

Diesel fuel has a tendency to foam, this is more noticeable with self bleeding system and high flow return lines, normally the returning fuel, which help cooling the injectors, return to the tank at a higher temperature than the fuel in the tank thus promoting foaming. Aerated fuel in a top pick-up can create an air lock. Also in bad weather with a low tank it is possible for air to enter a top pick-up and be trapped. For the above reasons when it is feasible designers tend to prefer bottom pick-up. A bleedable water and sediment trap at the bottom of the tank will be part of the design.
Fuel distributors recommends than diesel in stand-by generators be replaced every 3 years. I normally bleed by gravity the boats tanks every year. After filtering it I reuse it in my tow truck. In the case of a leak on the supply line, a top pick-up is no much safer than a bottom pick-up because it will siphon the fuel out of the tank. A top pick-up is also more vulnerable to air ingress at the top coupling.
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