Fuel Tank-Insulated or not?

[Fleetwin]

I've been looking for a replacement fuel tank. Around 35 gallon.

I see that some are "insulated" while others are not.

Other than the obvious, what does insulating a fuel tank do for you?

 

[jrttoday]

"in the days of old when Knights were bold, and the King's word was law" lol I remember some guys I used to run with coiled their fuel line through a coffee can. Put ice in it to cool the fuel. "Redneck Science" lol Kinda makes sense if you're looking all out performance when most of us are out there basking in direct sunlight all day

 

[shrew]

Gasoline expands when temperature is increased. Since fluid is measured by volume, the specific gravity (density) will vary as temperatures rise and fall. A typical gallon of gasoline will vary from approx. 5.93 lb/gal. to 6.14lb/gal. depending on temperature. Obviously the colder it gets, the higher the weight per gal. as the fluid contracts allowing more fuel to fit the same space.

I believe an insulated tank reduces the fluctuations. We see i tin the boat yards up north every spring. Someone tops off their tank in late fall, when its cool out, just prior to hauling the boat, then in the spring when the temps start to warm, gas begins puking out of the fuel tank vent as the fuel in the tank is warming up and expanding.

 

[H20Rat]

"in the days of old when Knights were bold, and the King's word was law" lol I remember some guys I used to run with coiled their fuel line through a coffee can. Put ice in it to cool the fuel. "Redneck Science" lol Kinda makes sense if you're looking all out performance when most of us are out there basking in direct sunlight all day

In many cases that actually ended up costing power! Liquid fuel isn't very flammable, you need it to turn to a gas by the time it makes it into the combustion chamber. Cold liquid isn't very conducive to making that transition, so you end up with raw fuel droplets that aren't burnt up. Worst case is that you have droplets large enough they hit the spark plug and bridge the gap, causing a misfire. (not likely with EFI but can happen with a carb)

In any case, yeah I"m thinking it is for the reason shrew mentioned, temperature insulation to smooth out changes.

 

[roscoe]

I've been looking for a replacement fuel tank. Around 35 gallon.

I see that some are "insulated" while others are not.

Other than the obvious, what does insulating a fuel tank do for you?

Other than the obvious?

What would that be?

Insulated or not, within a few hours, both an insulated and non insulated tank will be at the same temperature.

Now, an insulated tank may not acquire as much condensation on the outside when going from cool to warm humid environment.

So, if the tank will be in an area that you don't want condensation dripping, insulation may be beneficial.

In most boats, the tank will be open to the bottom of the hull and/or the bilge, so it won't matter.

Take a look at the installation instructions that come with a new fuel tank, and you will see that most call for the tank to be secured, but not to foam it in place.

 

[jrttoday]

smokingcrater could be, lots of people had gimmicks they try selling you on back then. Seems like not much has changed lol

 

[Fleetwin]

Related question.

My boat has a 35 gallon, in floor, fuel tank.

The floor is aluminum and I have it out exposing the tank. While it's only 35 gallons, it's enormous.

I am going to remove the tank and test it for leaks. It doesn't seem to have any but I constantly smell fuel. The lines and fittings are good.

Do plastic tanks have a tendency to "off gas"? Weird, but I smell it more the cooler it gets.

 

[dingbat]

Related question.

My boat has a 35 gallon, in floor, fuel tank.

The floor is aluminum and I have it out exposing the tank. While it's only 35 gallons, it's enormous.

I am going to remove the tank and test it for leaks. It doesn't seem to have any but I constantly smell fuel. The lines and fittings are good.

Do plastic tanks have a tendency to "off gas"? Weird, but I smell it more the cooler it gets.

You say the hoses are good. When is the last time you changed the fill hose? The last two tanks I checked for leaks had issue with the fill hose. Look at bottom of inside bend in hose. Hoses older than 7 years should be replaced.

A 35 gallon tank isn't enormous. I have two tanks. A 94 gallon main and a 54 gallon reserve tank on a 22' boat

 

[Watermann]

Related question.

My boat has a 35 gallon, in floor, fuel tank.

The floor is aluminum and I have it out exposing the tank. While it's only 35 gallons, it's enormous.

I am going to remove the tank and test it for leaks. It doesn't seem to have any but I constantly smell fuel. The lines and fittings are good.

Do plastic tanks have a tendency to "off gas"? Weird, but I smell it more the cooler it gets.

Yeah the size of belly tank it takes to hold 35 gallons does look pretty big, that's the same size poly tank I have in my Chief. If your tank was leaking it would be a very strong odor and gas might even show up in the bilge. I agree, pull the tank, test for leaks and buy some new feed, vent and fill lines.

 

[Fleetwin]

You say the hoses are good. When is the last time you changed the fill hose? The last two tanks I checked for leaks had issue with the fill hose. Look at bottom of inside bend in hose. Hoses older than 7 years should be replaced.

A 35 gallon tank isn't enormous. I have two tanks. A 94 gallon main and a 54 gallon reserve tank on a 22' boat

All the lines are actually off and the fittings sealed.

I now have the tank out, empty and now full of water-testing. So far, so good.

I just don't want to put a suspect tank back in this boat. You have to tear the entire boat apart to get to it.:blue:

 

[Watermann]

I now have the tank out, empty and now full of water-testing. So far, so good.

I just don't want to put a suspect tank back in this boat. You have to tear the entire boat apart to get to it.:blue:

The accepted method of testing a fuel tank for leaks is air pressure at 2 - 3 psi just so you know.

The same can be said of replacing the lines, you'd have to do a considerable amount of deconstruction to the boat too. Keep in mind that new low permeation hoses would be an upgrade over older hoses. If nothing else a new feed line that's always full of fuel would be a good candidate for replacement. If any of them are feeling like they have lost some flexibility then then they should be replaced.

 

[Fleetwin]

All the lines are actually off and the fittings sealed.

I now have the tank out, empty and now full of water-testing. So far, so good.

I just don't want to put a suspect tank back in this boat. You have to tear the entire boat apart to get to it.:blue:

Watermann,

Yup I knew about the air pressure testing. Says it right on the tank.

Anyway, great tip on the new type hoses. I planned on replacing all of them anyway.

By the way, did you put anything under your tank on the :Chief"?

My floor under the tank is elevated off of the hull and flat.

Thanks.

 

[Watermann]

To pad the tank I used 1/4" thick neoprene strips that were originally under the tank in the donor boat. You can get the same neoprene for padding in strips at Amazon.

 

[Fleetwin]

Thanks Watermann