foam around fuel tank ??

moparlvr4406

moparlvr4406

Active Member
Jun 29, 2011
4,462
Lake Monroe Indiana Fourwinds H31
Boat Info
1985 340DA
1966 SRV180
(2)1960 Sea Ray 600
(2) 1963 808 Cruise-a-bouts
Engines
twin 350hp Crusaders 4.0 Onan /
Merc 950 SS
Merc 650
Merc 1100
twin Johnson 40
I opened the can of worms in a decking repair yesterday
the center section over the fuel tank on my 240 was swelled up and soft
on the port side so I removed it...only to find a bunch of fuel soaked foam
the fuel leaks are now repaired...resealed some fittings and tightened some clamps
but I dug out all the fuel soaked material needless to say.
it appears some PO replaced the tank and shot the cavitiy full of that "Great Stuff"
foam.
is there a PROPER foam material to use around the fuel tank ??
 
I'm not a fan of closed cell foam around a tank. It holds water if you have a leak which can cause the tank to corrode from the outside in.

Is there anyway that you can mount it directly to the stringers without foam? Use spacer blocks if necessary?

Doug
 
I actually can't remember the last time I saw a tank surrounded in foam. Not saying it's not done, but all the Ray's I've seen I have never had it surrounded in foam. The tank will expand as gas is put in it - it needs room to "breathe". There are strap kits available - you can also use plastic L-channel to hold it in place.
 
It has straps suspending it already
so the foam isn't necessary :huh:

I figured it was for flotation or insulation of some sort...maybe this is just something a PO did just because ????

since the tank is suspended on straps should I dig all that crap out while I am in there ???
 
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It may have been something SR did back then - or it may have been something that the PO did. Dig out what you can - but don't go crazy. I would at least dig it out to the point that it allows the tank sides to expand as gas is pumped in. Even if it was there for flotation (and I don't think that it was), the little bit that you're taking out won't affect anything.

Wait... is this an aluminum or plastic tank?
 
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The foam may very well have contributed to the leaking. Aluminum sweats much more than plastic. The foam, right up against the metal would keep the moisture there. I would take away all the foam - at least as much so there is good air circulation around it - and good pathways to other areas.
 
the leaks were loose clamps at the fill hose and a questionable thread seal at the pickup tube
the tank is clean and shiny (top and down about 4"...havent seen the bottom)
I have noticed no real "fuel loss" or smell in the bilge.
 
Good. Hopefully you won't find any surprises. Al is, of course, much better than steel at resisting water-induced problems. But any time water lays on things, it can cause problems. Better not to tempt the boating gods!
 
I bought a 17' Pro-Sport brand new and decided to head off shore to do some grouper fishing. I stopped and put some fuel in it (the gauge showed full) and we proceeded off shore. About 5-7 miles off shore the motor quit. After some troubleshooting it appeared as though we were out of gas. After Sea Tow brought us some gas (very expensive gas I may add) we went back to the docks. I brought the boat in to see what was up. They told me the factory sprayed too much of the foam around the plastic tank and it pushed the tank upward right under the sending unit so it always showed near full. Lesson learned, never trust your fule gauge.
 
Lazy Daze said:
The foam may very well have contributed to the leaking. Aluminum sweats much more than plastic. The foam, right up against the metal would keep the moisture there. I would take away all the foam - at least as much so there is good air circulation around it - and good pathways to other areas.
Click to expand...

would it sweat with the insulation around it? It sweats because of the temp differences. would there be much of a difference? just asking!
 
You're correct - temperature difference is the culprit. It may, indeed, sweat less. But, any condensation that does appear will also linger longer :smt001. If the foam has any wetness to it (which is very likely in low lying areas in a boat (especially one that is kept in the water), that would also be bad.

Keep in mind that according to the OP, it appears to be a general purpose-type expanding foam which can absorb water.

I eluded to this above, but probably not well enough as I didn't think it would matter in this instance. While I have never personally seen any boat with a foamed-in tank, I do seem to recall reading somewhere (a while back) that it either was done or still may be done by certain boat companies (maybe larger SR's - I don't know). But, a special foam was used that would not absorb water. If the tank sides were completely closed off from the atmosphere, then it would not be a problem. But, I also seem to remember that some type of special coating (something about "coal" or "tar"?) is to be applied to the aluminum, first - I'm sure the OP would have noticed that.

You know what? I take back not seeing it done... As I'm typing this, I just remembered seeing it on an old SR bowrider and that the foam appeared very smooth looking. Also, being an aluminum tank, the part about the tank expanding is not really relevant - as it would be with a plastic tank.

To sum up... get rid of any inferior foam, especially if it is wet. If it's strapped down well enough - I would just leave it as-is.

If you wanted to pour some foam back in - first do some research and make sure it is still an acceptable practice. It may be - I just don't have enough experience there to say one way or the other. But, because the tank is "shiny", it certainly doesn't sound like it has any type of special coating on it - but again, I'm trying to remember back an awful long time ago regarding that coating.
 
The OP asked me by PM to read and comment, so here's my 2 cents worth:


Sea Ray uses closed cell expanding foam on larger boats as a sound deadener only, it isn't there for floatation since the USCG flotation requirements are for boats generally under 20 ft in length, but the flotation requirements for 1978 would govern here, and I don't know what they were. Expandable closed cell foam will eventually absorb moisture so it should never be used around or under an aluminum fuel tank because aluminum will corrode in the presence of moisture.

In this case, some previous owner who didn't know better and didn't take the time to research it (I have my political correctness hat on this morning, but the word "Idiot" comes to mind) used a home building product around a replaced aluminum fuel tank. This foam does expand to fill a void and will deaden sound, but it is also hydroscopic.....i.e. collects moisture.......and is flammable. That means that you have your fuel tanks neatly insulated with moisture and with a foam that will burn faster than the boat if it catches fire. If the boat is a keeper, you need to remove all of that foam. In fact, based on your description of the installation, to be sure you don't already have corrosion from the foam and where the tank was sitting, I probably remove the fuel tank, check it for corrosion, repaint it then reinstall it on some extruded PVC square tubing to give it an air space beneath it.

Most likely not what you wanted to hear, but you asked what I thought...............
 
fwebster said:
The OP asked me by PM to read and comment, so here's my 2 cents worth:


Sea Ray uses closed cell expanding foam on larger boats as a sound deadener only, it isn't there for floatation since the USCG flotation requirements are for boats generally under 20 ft in length, but the flotation requirements for 1978 would govern here, and I don't know what they were. Expandable closed cell foam will eventually absorb moisture so it should never be used around or under an aluminum fuel tank because aluminum will corrode in the presence of moisture.

In this case, some previous owner who didn't know better and didn't take the time to research it (I have my political correctness hat on this morning, but the word "Idiot" comes to mind) used a home building product around a replaced aluminum fuel tank. This foam does expand to fill a void and will deaden sound, but it is also hydroscopic.....i.e. collects moisture.......and is flammable. That means that you have your fuel tanks neatly insulated with moisture and with a foam that will burn faster than the boat if it catches fire. If the boat is a keeper, you need to remove all of that foam. In fact, based on your description of the installation, to be sure you don't already have corrosion from the foam and where the tank was sitting, I probably remove the fuel tank, check it for corrosion, repaint it then reinstall it on some extruded PVC square tubing to give it an air space beneath it.

Most likely not what you wanted to hear, but you asked what I thought...............
Click to expand...

I think exactly the same. Got rid of all the foam in my boat and I live happily now :smt001
 
thank you for your input Frank
and you are right...not what I wanted to hear...BUT what I needed to know
guess I am foam miner now....fix it right..once :thumbsup:
 
Be thinking plastic putty knife and a big-a$$ shop-vac.

The plastic putty knife won't scar the fuel tank and if you break up the foam, a 2-1/2" hose on a shop-vac makes it disappear quick.
 
Frank brought up a good point - as long as you're doing this part way, you may as well do it all the way to be sure the entire tank is in good shape.

Just a little encouragement... if the removable floor piece you took out was big enough, it's probably easier than you think to remove the tank. If it's mostly empty (or siphon the gas into your car), once you remove the straps you might get lucky and it will slip right out. It all depends on how well that "great" stuff stuck to the tank and how tightly it we
dged it in. Luckily I've only ever had to remove 3 gas tanks in my lifetime - but all times it was very straight forward and didn't take much time.

Frank once turned me on to a company called US Plastic. Check them out for the PVC angle/boxes.
 
this should be an easy pull...the hole is way big...good access from all directions and the foam is not sticking to the sides of the tank
but the tank has about 60 gallons in it...ah well ....I have an empty 55gal at work and a 12v pump :wink:
wish me luck on the bottom side of the tank
 
Jim... a pump that can make a spark? Frank may have something "politically correct" to say about that...:smt001

Although I suspect, Jim, that you made that comment a little "tongue in cheek"?
 
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