Fuel tank Size

[_laxmasta2039]

oh lords of the outboards [that kinda rhymes!],

my OB rigger's current fuel setup is a sully 6oz with a 1oz fixed on top of right in front of the transom. i would like to lighten this area up as much as possible, right now the CG is probably at >23%! also, it doesnt really seem worth the extra trouble of filling two tanks, having the exhaust pressure go through a hopper tank and so on for just one additional oz... would my boat [running the aforementioned ancient-but-hopefully-potent KB] be able to compete in heat racing running on just a 6oz fuel tank?

Joe

 

[waterbug]

No Gods here,

Isn't the purpose of the hopper tank on top to keep the CG low in the hull and keep fuel level with the carb for good flow????

If you take the tank off you must raise the 6 oz. tank up higher in the hull raising CG!!! bad for turns!!!

About all you could do is move it forward or go to smaller bottom tank! It depends on the run time.

 

[topfuel443]

Hey Joe, A pic would certainly help to see how its set up now, but I was always under the impression the hopper tank was to help keep down on the fuel foaming up (kinda like a baffle). Anyway depending on alot of things 6 oz. of fuel will be pushing it to the limit for mill time and a six lap race. Like I said that depends on how thirsty the engine is, is it ported like crazy? The temperature will have a lot to do with how much fuel you use, (the colder, the richer you will have to go, or if its hot outside that would help due to the leaner run condition, using less fuel) ther are alot of variables that affect fuel consumption. I use grims tanks on my outboards and they work great, Im at work right now so i dont know how much fuel the 3.5 tank holds but I know its more than 6 oz. probably mor like 8 to 10 ozs. (which is plenty)

~ James

 

[_laxmasta2039]

wish i could get a pic on but i cant..the tank is set up like this:

SIDE VIEW:

********

* 1oz *

* *

*******************

* *

* 6oz *

* *

* *

*******************

The hopper is taped onto the top of the 6oz.

I thought it would be easier to just have one tank, but if you guys think a hopper tank is a plus then i'll leave it on and see how it goes....

 

[topfuel443]

Joe, Ive run outboard tunnels without a hopper with no problems but have never run a outboard rigger, dont know what the difference would be if any. Id say if you have to use the exsisting tanks that came with it, use the hopper, if for no other reason than you will have alittle more fuel to run with. or if you have a 8oz sullivan plastic tank, or can get one, I wouldnt use the hopper if you dont want to. my .02 cents

~ James

 

[_laxmasta2039]

James=theirin lies the problem! i've got 3 6oz tanks, a 4 and that 1 hopper but no 8s....[not that a Sully fuel tank is a huge investment 7$ on tower] i'll probably run with the hopper for now and change if i need to once i get tuning....

thanks everyone for you opinions,

Joe

 

[synthon]

Please don't pay $7 for this tank at Tower! I'll send you a used 8 oz for free! It's in perfect shape. Email me privately.

Rick

 

[Propjockey]

Ya beat me to it, Rick.

 

[Slideblues]

Hey Guys:

Get with Grim for one of these and your tank and needle problems are over.

Think this one is 7.2 oz.

Gene ;D

 

[TomMoorehouse]

Gene...r

Your right Grim is a nice guy and his products work...

Tom 8) muha haha

 

[Jeff Torgalski]

Hey,

This post raises a few questions in my head....the general rules for a good fuel tank setup.

So far, what I've gathered is you should try to set the tank as high as possible so the engine draws the fuel, right?

What's so great about a hopper tank?

P.S. I noticed Grim's tanks are tall and skinny. I found a Hayes tank that has a similar shape, and it's alot easier to assemble than a Sullivan. I think they're great.

 

[GMC7]

New to the outboard/rigger sence, but in my Helicopter, experience, the i oz hopper tank did a couple of things:

1. Keeps the fuel from foaming making the engine run consistant

2. Gave me a visiual indication when the fuel was runing out (understand that you cant see it in a Tunnel hull.

3. By placing the the tank level with the carb it make easier needle adjustment.

My two Lincolns to the issue!

 

[toddzeller]

Joe,

On my .21 O/B riggers I'd stick a Dubro 4 and 2 oz as far forward as possible inside the tub, then mount a Sullivan slant 1oz on top of a piece of ply across the tub, back by the transom(if you run a rear cowl). Use 5/32" tubing instead of the 1/8" and large fuel line, and you won't have problems drawing fuel.

Just don't start you boat until around 1:45 or less on the clock. Otherwise you won't have enough fuel :'(

Todd

 

[bubba]

jo heres a pic. of JD's tunnell. do it like this

matt

 

[bubba]

darn i can get the picture to post :'( :'(

go to http://www.rcboatmodeler.com/RB/plans/fspb1200A3.asp

matt

 

[Slideblues]

This Pic?

 

[_laxmasta2039]

guys, [PJ and Rick]

thanks for the 8oz tank offers and i'd like to take you up on that if it turns out i need that extra oz of fuel, which is likely......i can give you a list of what i've got lying around to see if there's anything you'd like. Gene, that's exactly what it looks like now, almost thought that was a pic of my boat! the only difference is that i've got a 1oz hopper instead of 2 [or is that a 4oz with 1oz hopper?]

Todd,

i do have a rear cowl on it, but i dont think ,my boat's set up to have the CG as far forward as putting those tanks up there would be...though i did think of putting a 6oz in the back where the tanks are now and a 1oz hopper all the way in the front, but there's always the chance of leaky pipes? [imagine two servos and a reciever coated in sticky nitro residue! ]

Joe