Fuel tank install

[MikeyThumbs]

Hey everyone.. so I got my tank ready to go in this weekend but I had a couple of questions. FYI, boat is a 1984 Tournament 170, 30 gallon in-deck tank being replaced. Had it fabricated to match the old tank exactly..

1- The tank doesn’t seem to sit level in the fuel tank coffin area. It’s about 1/4” if not more lower toward the bow of the boat.. should I shim the front side up with neoprene to make it sit level? I don’t remember (or it was to shot to tell) how it was laid out beforehand and if it was pitched like this to begin with.. could this be pitched purposely, maybe to settle any sediment away from the pickup tube?

2- is there any other option besides wooden wedges along the perimeter of the tank to hold it in place? The wedges that were there were rotted and basically fell apart so I don’t even have them to use as a template.

any help or advice I’d appreciated as always!!

 

[Hookup1]

Is the new tank identical to the old tank?

There is no such thing as “level” on a boat. I would shim tank to be even off the hull/compartment. Then secure it.

 

[Fishtales]

I'd try to level it and even better with a small pitch toward the pick up. The sediment will move around anyway due to normal motion of the boat, I doubt a pitch will help at all with that.
You have a 30 gal tank, you def want the ability to get almost all the capacity out of it. A slight pitch toward the pick up would guarantee it.
I'd look at starboard or like plastic. I believe GW uses it today vs wood. You can notch pieces and really do a nice job without a ton of skill. Use adhesive and SS hardware to mount maybe consider small rubber pieces to isolate the mounts and tank. Ensure no other type of metal comes in contact with the tank - including the SS hardware. I think if you do this, your job will outlive the boat. Just my 2 pennies if I were doing it.

 

[Timcan]

I just finished installing my main tank as stated above Grady uses plastic/starboard wedges at least on my boat they did. I coal tar epoxied my tanks and glued(5200) 2 plastic strips to separate the tank from the deck. Anything the comes in contact with the tank should be glued on to prevent from holding moisture.

 

[DennisG01]

Yes, definitely glue strips on to raise the tank. You WANT air circulation - that's the key to aluminum staying good and not corroded. Same holds true for whatever you glue on. It MUST be glued 100% - including fairing the edges. If there are any gaps where the slightest bit of water can collect, that will lead to corrosion.

Depending on how the tank fits in the coffin, you may only need some upside down PVC L-channel to hold it in place. Glue a small block or neoprene pad where anything will contact a "hold down".

 

[MikeyThumbs]

Yes, definitely glue strips on to raise the tank. You WANT air circulation - that's the key to aluminum staying good and not corroded. Same holds true for whatever you glue on. It MUST be glued 100% - including fairing the edges. If there are any gaps where the slightest bit of water can collect, that will lead to corrosion.

Depending on how the tank fits in the coffin, you may only need some upside down PVC L-channel to hold it in place. Glue a small block or neoprene pad where anything will contact a "hold down".

Got it. So in the coffin there is about 2” of space each, on all 4 sides.. there were wooden wedges in there from the factory but wondering what else I can use to secure the tank from moving side to side…

 

[Hookup1]

Got it. So in the coffin there is about 2” of space each, on all 4 sides.. there were wooden wedges in there from the factory but wondering what else I can use to secure the tank from moving side to side…

I have seen tanks that have right-angle pieces of HDPE machined as blocks to keep the tank down in place and also blocking to control side-to-side.

 

[MikeyThumbs]

I have seen tanks that have right-angle pieces of HDPE machined as blocks to keep the tank down in place and also blocking to control side-to-side.

View attachment 29577

That would be perfect, I just don’t know where to get something like that?… any ideas?

 

[DennisG01]

That would be perfect, I just don’t know where to get something like that?… any ideas?

Mcmaster Carr will have it.

You can probably make PVC board from Home Depot work - even if you have to use two pieces and first attach a piece to the stringer.

 

[MikeyThumbs]

turns out I need to raise the lower side of the tank about 1” to 1-1/8” to bring it level or add slight pitch toward the pickup. What I think I am going to do for that issue, is place strips of wood on top, (coated with epoxy) perpendicular to the stringers and 5200 them down under the lower side of the tank. Then I will use the neoprene strips between the tank and wood… my only concern is I’m afraid there will be an unsupported section of tank doing this though.

 

[Hookup1]

If you have a decent table saw and a drill press you should be able to make them. McMaster would have it but you may be able to order HDPE stock on Amazon or find a plastic supply house online.

I'm no expert on how the strips should be prepped or attached to the tank. This is a little Vodo "science". Lots of opinions.

 

[DennisG01]

Oh... wanted to add... while Mcmaster will have the HDPE stock, I think if it was me that I'd use the PVC trim board. It's easy enough to use 1" trim boards and make them thicker since you can use PVC glue to put two or more together.

Personally, I don't think I'd go to the trouble of trying to pitch the tank. I've never seen a manufacturer do that so it makes me wonder how much it really matters? I suppose it can't hurt, though.

If you're going to pitch it... use the PVC trim boards. You can run the shims laterally or longitudinally. If you run the longintudinally, you can glue a couple together then cut it into a long wedge shape. If you run the laterally... make sure you leave a nice gap in the center... but then you make different thicknesses of shims from front to back.

If you didn't already, take note to what I said above about 100% and fairing.

 

[Hookup1]

I wouldn't shim the tank for a 1/4" pitch. Tank angle will be affected more by how the weight is distributed. When you are really low on fuel you need to keep the bow up. This was me earlier in the year. I didn't get stranded but lesson learned.

Running out of fuel

Had a interesting problem the other day getting fuel. Running off one tank to each engine. Both tanks low but had at least 1/8 tank. Ran to the marina that has a 1/4 mile long no-wake zone. Fueled the boat and went to start the engines back up. No start on either one - both crank fine. After...

www.greatgrady.com

See if GW has the HPDE blocks available. Not sure the PVC is strong enough and not sure it will stand up to fuel without melting.

 

[seasick]

Remember that your hull will sit differently when the tank has gas in it and you are at the helm. If you will raise the front of the tank,make sure that you will still have clearance for the fill and vent fittings and hoses.
You may be overthinking the install. If you want to be sure that there wont be a problem, set up the tank on the ground and shim it to match how it would sit in the tank coffin Then add water in two or so gallons increment to see if the pickup will suck water or air. Go from there on the spacers.
With regard to the 5200, you should put a decent ( a lot) of 5200 on the tank surface that will sit on the support. That is put there to insure that moisture will not seep in between the tank and the support. Moisture can lead to tank corrosion. With respect to a rubber type of material, I am not sure if neoprene is a good choice. Any material that contains carbon can lead to galvanic corrosion as the material ages and leaches carbon. Thin strips of fiberglass reinforced strips ( similar to the fiberglass panels they see for bathrooms or commercial kitchens isolated form the tank by 5200 would be better.

 

[MikeyThumbs]

Remember that your hull will sit differently when the tank has gas in it and you are at the helm. If you will raise the front of the tank,make sure that you will still have clearance for the fill and vent fittings and hoses.
You may be overthinking the install. If you want to be sure that there wont be a problem, set up the tank on the ground and shim it to match how it would sit in the tank coffin Then add water in two or so gallons increment to see if the pickup will suck water or air. Go from there on the spacers.
With regard to the 5200, you should put a decent ( a lot) of 5200 on the tank surface that will sit on the support. That is put there to insure that moisture will not seep in between the tank and the support. Moisture can lead to tank corrosion. With respect to a rubber type of material, I am not sure if neoprene is a good choice. Any material that contains carbon can lead to galvanic corrosion as the material ages and leaches carbon. Thin strips of fiberglass reinforced strips ( similar to the fiberglass panels they see for bathrooms or commercial kitchens isolated from the tank by 5200 would be better.

Could it be possible that the boat has most of the weight at the stern where the outboard sits, so the tank pitching toward the bow will keep the weight distributed more evenly? I didn’t remove any type of shims and can’t remember if the original tank was this pitched this much, but I’m assuming GW had it this way from the factory for a reason.

The reason why I’m using the neoprene/rubber strips is because the shop that fabricated the tank recommended this was what I should be using.

I do plan on opening up the floor hatch at the end of every season to inspect the tank and make sure everything looks good, so if I notice anything looking like it’s starting to corrode it will be changed immediately.

 

[DennisG01]

Good question about PVC vs gasoline. I don't know the definitive answer, but I'm thinking it should be fine. A little more research would be good. The PVC is very inexpensive and easily attainable - a definite plus. But Mcmaster should have the HDPE.

Although... if you're getting gas on the trim boards then there are much bigger problems at hand!

Oh... it just dawned on me... I've seen PVC L-channel being used to retain gas tanks on many, many boats. The PVC would be fine. Besides, it's not like it's immersed in gas.

Mikey, back to the pitching... are you saying that when you removed your existing tank there was pitch added to it by GW? This whole time I thought you were asking about doing that because it was done with the first tank. If that's the case... as noted above... don't overthink this. Plop it in and be done with it.

 

[MikeyThumbs]

Good question about PVC vs gasoline. I don't know the definitive answer, but I'm thinking it should be fine. A little more research would be good. The PVC is very inexpensive and easily attainable - a definite plus. But Mcmaster should have the HDPE.

Although... if you're getting gas on the trim boards then there are much bigger problems at hand!

Oh... it just dawned on me... I've seen PVC L-channel being used to retain gas tanks on many, many boats. The PVC would be fine. Besides, it's not like it's immersed in gas.

Mikey, back to the pitching... are you saying that when you removed your existing tank there was pitch added to it by GW? This whole time I thought you were asking about doing that because it was done with the first tank. If that's the case... as noted above... don't overthink this. Plop it in and be done with it.

I ordered the HDPE bars in various thicknesses and will make up the blocks with that and be done with it, as far as support goes..

As for the pitch, yes when I removed the old tank, I didn’t it modify the stringers in any way other than a thin layer of fiberglass to cover a small crack. The new tank is an exact replica of the original… from the floorboard, it measures a couple of inches to top of the tank on one side and almost 4 inches on the other (closer to the helm).. the more I think about it the more I think it was designed to be this way from the factory for weight distribution reasons..

30 gal is a decent amount of fuel, not sure how long it will last with a 70hp 2 stroke, but it’s not like I’m planning on going offshore with this boat. it will be for bays and local inlets mainly. I won’t be running the tank low regardless, so it shouldn’t be an issue with being pitched away from the pickup, I think..

Ill try to get some pictures up if I can sneak onto the boat before my wife catches me I promised her no boat or fishing stuff for Mother’s Day weekend

thanks again for the replies!

 

[MikeyThumbs]

Shhh ..

 

[DennisG01]

30g on a 17' boat with a 70HP... yeah, that's PLENTY of gas.

When you're running the boat, the attitude of the boat will bow high.

I won't say anything

 

[MikeyThumbs]

30g on a 17' boat with a 70HP... yeah, that's PLENTY of gas.

When you're running the boat, the attitude of the boat will bow high.

I won't say anything

I think I’m going to just shim the low side of the tank up about 1/2”.. 1” of pitch seems so drastic and unnecessary to me when thinking about the physics of liquid. Then again I’m no boat engineer by any stretch….