Fuel tank pick up tube? how long?

[findinghomer]

first of all my boat would not start, as suggested by a member here, i check the fuel tank pickup hose. sure enough it was broken. thing is, somebody patched it about three inches from the fitting, and the patch broke. so im thinking oh no biggie, i just eliminated the three inches and connected the tube at the fitting where the patch once was (so i lost a few inches of hose)..... took boat out, got stranded. starving for fuel


now today after diagnosing it, i found fuel is not gettin picked up, and sent to the engine ( i did put a new primer bulb on it) . BUT if i take the fuel sending unit out, and the pick up fitting off of the tank, pull the hose out and let it dip right in the very back of the tank it (where its visible) picks up fine, and runs great.?? the pick up tube is now about 3 and a half feet long, stuffs way up into the tank under the floor, with a nice angle cut on it. but it seem like gas is not able to get to it when its crammed all the way in up the tank like that. so i guess my question is, how long should the tube be? and wouldnt it be ok for it to be very short and sit down in the fuel right at the back of the tank, (close to the fuel pick up) fitting? or is it supposed to be long, and tucked toward the front of the boat (furthest away from the pick up fitting)? could that angle cut be laying upward inside the tank, causing fuel not to spill into the hose ? think im gettin somewhere just need some expert advice, thanx

ps this is a 125 with a 30 gallon built in tank

 

[kend301]

Re: Fuel tank pick up tube? how long?

I think you may have 2 problems , First of all if the pickup tube in the tank is very flexable it may be kinking if you are having to force it in. Also the pickup tube should be it the back of the tank so under acceleration with the bow up fuel will want to go to the rear of the tank . Remember fuel has it's own gravity within the tank and will try to remain level with the horizon also the small amount of g forces you pull in a boat will make it slosh to the rear of the tank. So in theroy with 1/2 tank of fuel and the pickup in the front of the tank under wide open acceleration with the bow up you could run the pickup dry ...This is why we run fuel pickups on the right rear of race car tanks , acceleration kicks the fuel to the rear and despite the banking on a track , g forces slosh the fuel to the right side of the tank ... Just my thoughts

 

[Lone Duck]

Re: Fuel tank pick up tube? how long?

I had a similar situation with a used aluminum tank I picked up for my boat. I had a long hose 1/2 the length of the tank and the fitting leaked where it entered the tank. I removed the hose and drilled the hole in the fitting to accept a 3/8 copper tube angled on the bottom. Inserted the tube straight down till it hit bottom of the tank , then lifted it 1/4" thinking that if I got moisture in the tank that I would not suck it up and contaminate my system. I then used the plastic epoxy putty to seal the copper tube to the fitting ,and the fitting to the tank where it was cracked. I also installed a water filter in the system between the tank and the primer bulb. That was 3 years ago and have not had a problem.

 

[findinghomer]

Re: Fuel tank pick up tube? how long?

exactly kend, in fact what i did was get a new hose, approx 6 in in length just enought to go straight down to the bottom of the tank. I put the pick up filter back on it and it runs fine.... your theory is exactly same as i was thinking, gas will almost always be forced to the rear of the boat, whether under acceleration, or on the boat ramp.

Only thing that made this an issue for me, is why the stock hose was sooooooooo long and curled to the front??? although there were no kinks, with this stock hose, once my fuel gets pretty low, but not empty, im basically losing access to all that fuel. i just figured there might be a reason for this long tube, so wanted to be sure before i take it out again this spring. in the garage though, my new contraption works wonderfully.

 

[kend301]

Re: Fuel tank pick up tube? how long?

Glad you agree , I was working on the fuel system today on my 14' jet boat and pulled the pickup so I could see what it was .. Just like you have set up , Straight down , 7" long , 1/4 off the bottom , angle cut at about 60 deg to pick up all the fuel and not vacuum lock to the bottom of the tank ... IN the rear of the tank.
My only thought to the stock length of your line is that they intended it to come all the way around to the back of the tank , The hose looped toward the front of the tank would act as a baffle once fuel got very low and might help you suck up the last few drops just before running out.... But why ever take that chance as these motors will burn a piston in a heartbeat from lean fuel

Or it could be a case of an idiot putting things together , I had one "experienced" crew member that put the pickup in the left rear on a Charlotte car and started running out of gas coming off the corners after 15 laps ... Perhaps someone just put a bunch of line in that knew no better .

 

[O.T.Water]

Re: Fuel tank pick up tube? how long?

FYI, Just extra info. I recently had a fuel starvation problem and didn't realize how many different things could cause it. Finally found a sticky anti-siphon valve attached to my fuel pickup. That I replaced and problem solved. What I thought was different was the pickup tube. It was HD aluminum all the way to the bottom of the tank with an inverted V notch at the bottom. I thought that design was well thought out. A straight angle cut would finish higher, matter a fact twice as high as the V notch cut. I can suck my tank almost dry. I need almost every drop with only 18 gallons. Someone was thinking. O.T.

 

[bob johnson]

I am fabricating an aluminum tank now. I have taken a few aluminum tanks apart to see how they work....I think you see a lot of plastic tubes because the depth of each tank varies... this way you can insert it and measure how much to cut, then install it and be good to go. I guess some people have just forced the tube in with out fitting and as such the tub lays on the bottom or might even curve upwards! I found one tank that had two V notches cut perpendicular to each other on the very end of the aluminum tube... and it was welded in place!...that's what I am going to do with my tank... Ill fit the pick up tube all welded in place before I weld the small end of the tank on!!!

the tank I took apart last week had an aluminum fitting head with a plastic tube and a crimped screen on the end...and it went to within a 1/16th" of the bottom.. and it had debris all around the screen..... Id rather suck up debris and have it clog a fuel filter, that I can easily replace, than my tanks pick up tube!!

bob

 

[GA_Boater]

An oldie, Bob.