Higher capacity topside tanks instead of 6gal portables?

[KC8QVO]

I am looking at getting a pair of topside tanks in the 15gal range. In the past I've always used portable 6gal tanks. My concern is all our motors that run them are 2 strokes with pressurized fuel systems. The ports on both the motors and tank are 2 prong. I see all the tanks these days have the 1/4" threaded coupler. Is there anything I should be worried about with the pressurized fuel system? Or just make sure I get the right end for the motor and attach the line to the tank with the 1/4" NPT barb?

Would there be any way to install a switch between the two tanks so I can run one line and flip a switch to swap tanks instead of swapping the hoses? Or is the pressurization not going to work through a switch?

 

[Chris1956]

Pressure tanks have two lines. You will need twin 2 to 1 fuel valves, and some way to seal and pressurize the new tanks. Maybe it is time to install a fuel pump on your motor?

 

[KC8QVO]

The lines on the tanks now are single lines with a pump bulb, the connectors have 2 ports though. Im not real sure how it works. The main motor is a 25hp, the others are a 9.9 and 4. All 3 are the same fuel line.

 

[JimS123]

You can modify all 3 motors to handle a single hose tank. I wouldn't modify the tank to take a double hose fitting because who knows if you could develop enough pressure with that large a tank to make it work properly.

Personally, I would stick with the 6 gal tanks and just buy a couple more if you need more capacity. Three little tanks are easier to stow than one big one.

 

[KC8QVO]

I have 2 6 gallon tanks now, 3x 5 gallon jerry cans, and a 2.5 gallon jerry can. I want less tanks on the boat and more fuel. I had 3 6 gallon tanks but one of them split last winter and wasn't holding pressure this spring so we pitched it. The other 2 tanks are around the same age so who knows when they are going to break too. With all the tanks and cans I can use now that will barely get me where I want to get to so boosting the size of the main tanks will give me that much more range and security. I need to run the other motors and see what the fuel consumption rate is so I can run some range calculations. I'd like to have enough reserve capacity that I can limp home on a spare motor if I have to - and I may be 60-70 miles out.

It looks like I can get a 12 gallon top side tank without getting in to the permanent mount ones that are twice or more the price, so that might be the route to go - a couple or three of those, like the Moeller 630012LP http://www.moellermarine.com/afterma...le_fuel_tanks/

I was at (a store whos name if I type gets asterisked out, otherwise known as kabelas spelled with a c) today and they had an Attwood 12 gallon tank. I read the label on it and it said that the tank was designed to balloon out/blow up. This leads me to believe that the "venting caps" seal well enough that they may work in a pressurized application? Maybe they are like a check valve and let air in but not pressure out?

 

[undone]

This is a little confusing, or you may misunderstand what you are looking at. What year are your motors?

 

[KC8QVO]

The main motor I use is a 1993 Johnson 25hp 2 stroke. I do not know the years of the others. The 4hp is older and the 9.9 is newer. All 3 motors use the same tanks now. When I have done my long runs the 9.9 is my spare.

 

[roscoe]

OK, your motors do not use a pressured fuel system.
Those would be found on pre 1964? 1960? motors, and they have 2 hoses running to the motor.

You can use any new top side tank, as long as you keep it topside, not below deck, not in an enclosed cabinet or storage area..
Attach the appropriate connector to the hose.

Yes, under the new epa rules, the new tanks with the new vents, will allow air in, but not allow fumes out, supposedly.

 

[82rude]

yup ,roscoe.the op is misinterpting the prongs .if you look closely 1 prong has an opening to accept fuel while the other is solid and is for attachment only.also as far as I know there was never a 9.9 pressurized to begin with.to the op.as roscoe says you do not have pressurized tanks or motors.on the 12 gallon moller which I have and all plastic tanks have the cap has a vent that you pull up .in order for you motor to run properly it needs to be opened.i forgot to open the vent on mine once and the etec 60 almost collapsed the tank in half.id imagine with your motors you,d probably just stall out as the fuel pump on those motors is relatively weak as compared to the etec which is fairly powerful.

 

[KC8QVO]

If the fuel system isn't pressurized then why is there air escaping from the tank when I go to open the cap after running? And why did the motor not run when I put the split tank on before I found it had a split?

 

[Chris1956]

Gasoline creates pressure when shaken. This is what you hear escaping from your fuel tanks. As was said, Johnny/rude motors after 1959 all have fuel pumps, and use a single line to supply fuel. Any new fuel tank will work just fine with your Johnnyrude motors newer than 1959.

What body of water do you operate on?

 

[Chris1956]

BTW - you should open the fuel tank vents just before you start the motor, and close them at the end of the trip.

 

[82rude]

If the fuel system isn't pressurized then why is there air escaping from the tank when I go to open the cap after running? And why did the motor not run when I put the split tank on before I found it had a split?

a pressurized system has 3 prongs not 2 .one is for gas to flow to the carb and one is for low pressure air to flow to the tank.the 3rd prong is for stability again.the simple fact that the gas is agitated in the boat will create low pressure itself and so will exposure to the sun.if not vented properly.trust us theres no way you have a pressure system with those 3 motors and their years.also a pressure tank will have a button that you push to prime the motor.for start up not a bulb .

 

[JimS123]

Your first post cornfused us - you do not have old motors, you have new ones.

Go ahead and buy any thing you want. Plastic tanks expand and contract - that's why you had one split. Buy metal tanks ad you'll be good to go way beyond the life of the boat.

 

[Frank Acampora]

And it's not air escaping after running. If you ran with the vent closed, it is air rushing back in. so you must run with the vent open.The fuel pump on the engines can pull enough vacuum to collapse a plastic tank in the worst case At best, the engine will starve for fuel eventually and stall.

 

[KC8QVO]

a pressurized system has 3 prongs not 2 .one is for gas to flow to the carb and one is for low pressure air to flow to the tank.the 3rd prong is for stability again.the simple fact that the gas is agitated in the boat will create low pressure itself and so will exposure to the sun.if not vented properly.trust us theres no way you have a pressure system with those 3 motors and their years.also a pressure tank will have a button that you push to prime the motor.for start up not a bulb .

And it's not air escaping after running. If you ran with the vent closed, it is air rushing back in. so you must run with the vent open.The fuel pump on the engines can pull enough vacuum to collapse a plastic tank in the worst case At best, the engine will starve for fuel eventually and stall.

I am really confused now.

When I put the tank on that was split, before I knew it was split, the first thing I noticed was the primer bulb was "loose". It never felt like it was getting tighter, which it should based on the others. Then when I started the motor it ran a bit, I got up on plane, and the motor quit. Then I repeated the process and same thing - motor quit. I found it would run if I kept priming the bulb, but I wasn't going to do that all the way home. That is when I got to looking closer at the system. I swapped tanks again to another one and the motor started right up and I got home. Afterwards I poured the gas out of the split tank in to a bucket (cleaned out) and transferred it in to one of the non-split tanks. The tanks also bulge out when in-use too, there is no worry of the tanks collapsing.

So what you guys are saying doesn't add up. I'm not saying you're wrong, but what I've experienced just doesn't match what you're saying and all of my experiences are the reasons why I posted my original question. Why won't the motor run on a split tank? That would be the equivalent of loosening the filler cap = freely lets air in, would it not?

 

[Chris1956]

It is hard to guess what damage is in the split tank. I therefore cannot give you an answer. Perhaps there is an air leak in the fuel line or pickup. The real question is whether the motor will run on a good tank. Toss the damaged tank and move on...

Remember, open the tank vent when you start the motor and close it at the end of the day...

 

[Chinewalker]

All of your motors have fuel pumps. NONE of your motors require a pressurized fuel system. Period. Regular OMC/BRP steel tanks will build up pressure when sitting in the sun or on any warm day - gasoline easily expands (and vaporizes) and contracts with temperature variations. The steel tanks have one-way vents. As fuel is pumped out, air is let in. Plastic tanks typically have a vent in the cap that lets air in and out. They can also be prone to bulging and splitting if left unvented on a hot day.

As noted above, simply get a standard fuel tank of you desired size and configuration, plumb it with your standard fuel line and be done with it... Note that if you get a "built in" tank, it will need an external vent over the side. If your tank is considered portable (even if it is 12-18 gallons) it will likely have some other venting method, usually through the cap.

 

[KC8QVO]

OK. Thanks for the info. Good point about the "permanent" tanks and venting. It looks like the biggest tank I can get that is still a "portable" is 12 gallons. So I may get 3 and call it good. I am looking at getting a bigger boat and will be able to use them there too. Does anyone have experience with the 12gal Attwood tanks? I was at kabelaz again today (different location) and got to looking at the fuel port. It sticks up high and looks to me like it would get broken off real easy. The Moeller 12gal looks more robust.

 

[Chris1956]

Gee, 36 gallons of fuel for a 25HP motor is a lot. You will be able to run at 3/4 throttle for 24 hours straight or so. That would last the average fisherman a month or more. Are you sure you need that much fuel?