1988 20ft Overnighter 204-C Fuel Tank specs

[BlueComet]

From some research on GG an other sites, it looks like my Grady's OEM was a 65 gal tank.

Unfortunately, my boat came with a 52 gal Moeller 32552 (FT5299) poly tank that I can get barely 25 gal into before gas starts coming up out the vent during filling.
I suspect it has to do with the fill/vent configuration, and my tank never has a chance to fill up beyond the first baffle before coming out the vent (path of least resistance).
My tank's fill port and vent port are both in the aft section, a photo can be found here: https://palmerpower.com/moeller-32552-52-gal-below-deck/

Here's a photo from last time I had this hatch opened up. The elbow was necessary due to the port being so close to the bulkhead, it's not ideal but fuel safe (from racing parts store). I'm trying to get back to a more "stock" configuration without all the "hackery."


For any 80's Overnighter owners out there, can someone please help answer the following questions for me, so I can get a baseline of what's "normal" in design?
1. Where does the vent come out? Mine's on the transom stern-face, just above the swim platform/ladder on port transom
2. Where is the fuel fill? Mine's near the vent, on top of transom, on port side above the swim platform
3. Can anyone supply a drawing for the 65 gal original tank? I've found them for the 80" long variant (larger capacity), I'm okay dropping in the 63" 65gal and reducing scope of this project.

I'd rather stick with a stock poly tank for ease, any recommendations on a stock moeller that works in this particular boat? If so, please let me know where fill and vent come out on yours also.

I'm in Boston area, if someone knows where to get a good used (not junk) metal tank I'd be amenable to that too.

Thanks in advance for the assist, we're just starting up boating season in NE, although it's still hat and gloves weather on the water from what one of my club-mates told me yesterday.

 

[Hookup1]

Start with going to GW site and find your owners manual. Older boats and smaller ones (you have both) are combined into one manual. See what you can find out from there.

Also call GW customer service. They are quite helpful. Get your questions in order first before calling.

When you are filling the tank how "level" is it? If the bow is high it will make it harder to get the fuel in. There is no vent on the forward end.

Last I would call Muller with the model number of the tank. Discuss the baffle" theory" with them. I'm not sure about that one.

Can you live with a 52 gallon tank? You could switch to another tank and still have this fill problem.

Is this a single engine? I see two small hoses. Is one pickup and one the vent? Are you sure the vent is not a pickup? Snake the vent hose.

Not much you can do with the fill hose. May not be the problem anyway.

 

[BlueComet]

Hookup,
Obviously you don't own this boat, but that's okay.

The boat isn't completely level. It never will be. I'd have to add 500 lbs to the bow and that's not going to happen, not fueling up with 3 people on the bow of the boat either. That's a hack, not a solution.

My "baffle" theory is probably wrong, there's likely no baffles. Doesn't change the symptoms.

Yes single engine, one's the vent, one's the pickup. The fill and vent hoses are correct. Had the boat repowered and re-transomed and they connected correctly too. It's the design of the tank, with the fill and vent co-located at the aft which is lowest part, it makes sense (liquid takes easiest path).

Got the drawing from Grady, attaching here since I'm not the only one looking for viable replacements on this forum or even THT. Hopefully that saves others time I spent, thats why this forum exists. The original drawing shows the vent toward the boat, not the stern, which makes sense. Fill, pickup and sender are aft, pickup should be at lowest point to maximize usable fuel capacity.

Short in short, this 52 gal tank is just wrong config for the boat. I can live with 52 gal or even smaller, but all that's useless when you can only get 20 gal in at most. The point is to get >20 gal in and not spill out when filling.

I've done a lot of homework on Moeller (and even Kracor) offerings to get into the length/width/height config with the vent and fill at opposite ends, and there just isn't anything out there that I've found. I was hoping someone else had a solution to save me the hours of research. Hopefully this will help someone else not waste same time I did.

Supposedly Patriot Marine in NJ has a stock tank that matches GW's drawing. That's cool but shipping isn't cheap in 2024, I'll report back on my findings. Going to look into Wilson Welding in Salisbury MA and see if they can maybe help too (and maybe save $700+ in shipping). Welding World has the larger tank already designed, but for $1500 + $800 shipping, that's not a great option.

Moral of this story, cheaping out in boating repair doesn't always work well (function or long-run cost). Sucks that GW didn't use a design that supports a "stock" poly tank, so AL is likely the solution for these boats.

 

[DennisG01]

Plastic tanks are nice - but this isn't about plastic vs aluminum. That debate has nothing to do with this issue.

No baffles - but that also wouldn't come into play here since we're talking about filling up.

Yes, it doesn't help that the fill/vent are at the aft end. You may HAVE to put some weight up front if it's as bad as you say. That's a good idea to do, regardless of the tank issue. The boat shouldn't be THAT far bow high.

Why is the bow, apparently, as high as it seems you are saying?

Currently, your vent line could have a dip in it. Follow it and correct it.

You might want to consider re-routing your vent to a new thru-hull that is further forward.

Another consideration is to install a new vent fitting near the front/middle of the tank. I seem to recall seeing pie plate kits for this... but it would be easy to make your own, too.

 

[Hookup1]

I'm not convinced changing the tank out will fix anything.

I'm going with vent hose being the cause. Did you have this problem before the re-power and transom work? A long run with a belly close to the tank would cause burping problems but not a 1/2 tank fill. I would remove the existing vent hose and install a temporary hose - then try to fill the tank up.

I wouldn't expect your tank to be completely level - just want to get an idea how out-of-level it is. Could it really be trapped air in the front of the tank. It would have to be extreme.

Can you see the fuel level through the tank walls? If so can you see the air bubble? I'm going ask a stupid question for diagnostic purposes so get don't get insulted - is it possible the tank is full? Pull the sending unit and look. While you are in there use an endoscope camera to see in there is any debris in the tank. I saw one where the tank builders left a nitrill glove in there.

The fill hose elbow may be problematic and require slow filling but it won't prevent filling the tank.

I would try is to remove the vent connector from the tank. Just to see how far the vent extends into the tank. I don't know how the make this connection on plastic tanks. Just to make sure they didn't do something wrong when the tank was built. It's really the only thing I can think of that could be wrong with the tank. I did my tanks last summer. I believe the pickup tube is welded to the fitting you see here. My vent is welded to the top of the tank.

 

[seasick]

If that is not the original tank, it is possible that the original had the fill and vent fittings forward and not aft as it is now and that the new routing of the vent line is not correct. There may be a dip in the vent hose that is holding fuel. The vent hose should never drop lower than the top of the tank level and should have an upward loop ( where the hose is higher than the vent fitting if the vent is external and not a combo fill/vent fitting.
In summary if you were to pour gas into the far end of the vent, the hose should drain down into the tank. Likewise it you were to pour gas into the vent hose at the tank end, that hose should also drain back into the tank. Finally, the vent outlet be it a clamshell or a combo fill should be higher than the top of the fuel tank at the bow end.

 

[Hookup1]

Looking at your GW print I see a vent at the forward end of the tank.

 

[Hookup1]

If it were mine I would stay with the existing plastic tank. Check exiting vent hose setup. If nothing fixes it install a forward vent.

Call Moeller and see what they recommend to install a forward vent in an existing tank. You could also pull the sending unit, make a hole up front, snake back, pull a vent into place and screw down tight.

When I did my tanks I pumped out thru pickup with automotive fuel pump then put dry ice into fill and later into sending unit hole. Then pumped out remaining fuel with non-sparking copper tubing attached to my fuel pump. Last inspect tank with endoscope. It's overkill for some guys but blowing myself up would slow the project down!

Here is my tankectomey from last year...

268 Islander Fuel Tank Replacement

Decided that this is the year to replace my 25 yo fuel tanks. No leaks. I plan to keep the boat. I'll document the process here. Pulled the hatch. This hatch was rebuilt a few years ago with Coosa board. Looks good and feels solid. Hatch was set with 3M 4000 - kept everything sealed. Some...

www.greatgrady.com

 

[seasick]

I am confused. When you say the tank only takes 20 gallons, what does that mean? Does the gas nozzle keep shutting off?
If the vent is aft and the tank has any amount of tilt aft, I can see how the vent would not function once the fuel level covers the vent fitting. In addition, fuel will probably back up into the fill line. Both of those issues would make filling the tank a difficult task

 

[Hookup1]

I am confused. When you say the tank only takes 20 gallons, what does that mean? Does the gas nozzle keep shutting off?
If the vent is aft and the tank has any amount of tilt aft, I can see how the vent would not function once the fuel level covers the vent fitting. In addition, fuel will probably back up into the fill line. Both of those issues would make filling the tank a difficult task

Let's see what to owner comes back with. I'm confused too what is happening when he is filling the tank. Slow down and backup.

 

[cham]

Let's see what to owner comes back with. I'm confused too what is happening when he is filling the tank. Slow down and backup.

We just ordered this exact tank (Moeller Belly Tank 52 Gallon) for our Tournament 190. Looking at BlueComet's tank schematic, part of the problem is the factory tank has the vent and fuel pickup on opposing sides of the tank. This Moeller tank unfortunately has all fittings one one side. It is the same case with our Tournament but short of shelling out 2k for a custom tank, there aren't any other options that fit our dimensions.

One key component here whether he's filling up on a trailer or in the water at a Marina, how is the tank resting on the hull. Since he has the fittings positioned on the stern side (we are doing the same), if in any of the fueling up situations the fittings are substantially lower than the opposing side of the tank, fuel will begin to be sucked through the vent hose before the tank gets even close to being topped off. Not only that but the fuel will begin to back up in the filler hose. If there's room, propping up the rear of the tank with more neoprene strips might serve to remedy some of those issues. If this isn't the case, my next guess would be the vent hose is either not installed correctly, or has an obstruction of some sort.

My concern for our tank is when underway and the bow is lifting, I worry the vent fitting will be submerged in fuel a lot of the time not allowing air in and creating a vacuum which bogs the engine. Can air still be sucked from the hose through the fuel even if the vent is covered? Our previous tank was a 40 gallon Moeller tank with the same fitting setup and we never had issues as far as I can recall, which surprises me. What are y'alls thoughts?

 

[Hookup1]

I don't really understand BlueComet's problem. That tank would have to be at a crazy impossible angle to only allow 20 gallons in.

All my tank connections are at the aft end of the tank. Fill, vent and 2 pickups. Never a problem. If you really want a vent up forward I'm sure you could install one. What is the tanks angle on your trailer and in the water?

 

[cham]

Once I have a chance I'll get a level on it here in a day or two (on the trailer). Might be a while before I can test the tank's level with the boat in the water. I would think the deck would be parallel with the water line if I can use that as a reference. The stern side of the hatch opening has a depth of 12 inches from the deck while the bow side has a depth of about 15 inches, so the fittings being in the rear should sit a bit higher than the other side of the tank. That also gives a little bit of leeway for when the bow comes up during acceleration, not all the fuel rushes to the rear immediately, that is, as long as the deck is parallel to the waterline when floating and not moving which I assume is the case.

Also something about the plastic Moeller uses, apparently sealants don’t take to it so adding in a fitting is very troublesome and not recommended.

 

[Hookup1]

Once I have a chance I'll get a level on it here in a day or two (on the trailer). Might be a while before I can test the tank's level with the boat in the water. I would think the deck would be parallel with the water line if I can use that as a reference. The stern side of the hatch opening has a depth of 12 inches from the deck while the bow side has a depth of about 15 inches, so the fittings being in the rear should sit a bit higher than the other side of the tank. That also gives a little bit of leeway for when the bow comes up during acceleration, not all the fuel rushes to the rear immediately, that is, as long as the deck is parallel to the waterline when floating and not moving which I assume is the case.

Also something about the plastic Moeller uses, apparently sealants don’t take to it so adding in a fitting is very troublesome and not recommended.

The deck should be parallel to the tank. The waterline may not be because of loading. I doubt you car going to find anything extreme about the angle.

You probably don't need a vent forward. You could install a fitting with neoprene gaskets and maybe a little Permatex fuel safe gasket/sealer.

 

[cham]

That might be possible. What like a threaded fitting with a gasket between the plastic surface and top BBC over of the fitting? I do know Moeller literally inserts the fittings while the tank is being molded. If that were done would plugging off the other vent be recommended or do some people run two vents for more peace of mind?

 

[DennisG01]

Also something about the plastic Moeller uses, apparently sealants don’t take to it so adding in a fitting is very troublesome and not recommended.

No, this is not correct.

Glue... no, HDPE doesn't take to glue very well. This has nothing to do with Moeller - all plastic tanks are made of HDPE. Neoprene gaskets work well, though. Just like the fuel sender that is screwed in on hundreds of thousands of boat gas tanks.

 

[Hookup1]

Two vents are overkill. If tank is relatively level just use the aft vent-most boats work fine that way.

If you decide to install a forward vent you will have to remove sending unit and pull in place.

 

[cham]

No, this is not correct.

Glue... no, HDPE doesn't take to glue very well. This has nothing to do with Moeller - all plastic tanks are made of HDPE. Neoprene gaskets work well, though. Just like the fuel sender that is screwed in on hundreds of thousands of boat gas tanks.

Yeah it is a little confusing because I've heard others say what you're saying but I don't think its just HDPE. They call it cross-linked HDPE which is like PEX. These are their own words:

Can I move the fittings on my Moeller fuel tank to make them work for my application?
No, our process does not allow us to move fittings that are molded in during the molding process. Moeller fuel tanks are designed for the recreational boating industry. We don’t have any data and do not recommend any modification be done to these tanks. Any modification or change is at the risk of the owner and also voids any warranty that accompanies the product.
Key Point: Cross linked polyethylene has unique properties which make it an ideal material for fuel tanks. These same properties make it difficult for sealant materials to adhere long term to any part of the tank. This is the reason that the tank fittings are molded into the wall of the tank. This also ensures a leak-free connection to the fuel tank.

 

[DennisG01]

Yeah it is a little confusing because I've heard others say what you're saying but I don't think its just HDPE. They call it cross-linked HDPE which is like PEX. These are their own words:

Can I move the fittings on my Moeller fuel tank to make them work for my application?
No, our process does not allow us to move fittings that are molded in during the molding process. Moeller fuel tanks are designed for the recreational boating industry. We don’t have any data and do not recommend any modification be done to these tanks. Any modification or change is at the risk of the owner and also voids any warranty that accompanies the product.
Key Point: Cross linked polyethylene has unique properties which make it an ideal material for fuel tanks. These same properties make it difficult for sealant materials to adhere long term to any part of the tank. This is the reason that the tank fittings are molded into the wall of the tank. This also ensures a leak-free connection to the fuel tank.

The cross linked part is a moot point. But you and I are saying the same thing. Glue doesn't work.

However, that's a CYA answer from a manufacturer. While I haven't had a need to do this, one can "burn in" a new fitting. But the tool to do it is relatively cost prohibitive.

But a bolted-in bulkhead fitting can work.

 

[cham]

Any recommendation on how to drill hole without getting shavings inside the tank?