12 gallon external fuel tank question

[C42480]

This coming spring we are doing a run from West Palm to Abaco about a 200 mile one way trip. I know how to plumb the tank in no issues there. The issue I'm having is finding a was to attach the 12 gallon tank to the rear deck. I would like to have something that is easy to take on and off and out of the way a much as possible. I do not really want a rack as I want to keep the weight of the tank as low as possible. Maybe adding pop up cleats or something. This will be on a 2018 FXHO cruiser. Any ideas or pictures will be greatly appreciated.

[K447]

I am also considering adding a Moeller 12 gallon ‘low profile’ fuel tank to the back of my 2017 GP1800.

The tank will cover the majority of the GP1800 rear deck.

I may put a traction mat or similar between the tank bottom and the rear deck, but otherwise I want the weight of the tank to be applied directly to the deck. Since it is a fuel tank with flat bottom the liquid weight inside should be well distributed across the deck area.

The question, as you have realized, is how to secure the tank to the rear deck. It needs to be able to withstand tremendous abuse while on the water. The tank will be stressed and yanked side to side, twisting motions in every axis, and slamming into wave after wave at speed.

It needs to not work loose, not be able to shift around, and definitely not break free.

Being able to easily remove it would be nice, but that must not reduce the ability of the thing to stay in place while riding.

Tank weight full of fuel will be close to 100 pounds. Plus whatever weight the hold down gear is.

My initial thoughts were to create curved flat brackets/hooks that reach underneath the side rails, similar to how a ski lift harness hooks under the side rails. Wide strong brackets, shaped to grab under the rub rails.

How to keep the external fuel tank from sliding backwards and forwards?
And resist twisting and bouncing motions that could work it loose over time.

[K447]

Moeller 630013LP 'portable' 12 US gallon, 45 litres
630013LP Low Profile, Low Permeability

24.5ÔÇØ wide x 17.74 x 10.82ÔÇØ including filler cap

I chose this Moeller model in part so it would be below the tow hook behind the rear seat. I want to be able to tow a disabled ski should the need arise and a taller fuel tank would get in the way.

[4-keeps]

https://www.jetskiracks.com/

RY racks are the next best option shy of a build in auxiliary tank (6-7 gallons) like I have, few of my friends & others I’m sure on GH. RT racks are build to suit the model ski. Options for the 12 gallon tank in middle, side tanks like the Rotopax tanks. I have several friends with the racks that have crossed the gulfstream with 100% confidence while using them. Keep in mind plumbed like most the auxiliary tank will drain first removing any of its weight. Hope this helps, Good luck on your crossing & trip.

Billy D

[C42480]

The racks are nice looking but I would like to not have one if possible. I was thinking of putting 2 cleats that retracts and using 2 ratchet straps with custom made webbing to keep the straps where I want them. I just want to see if anyone has done this and what there set up looks like.

[K447]

The racks are nice looking but I would like to not have one if possible. I was thinking of putting 2 cleats that retracts and using 2 ratchet straps with custom made webbing to keep the straps where I want them. I just want to see if anyone has done this and what there set up looks like.

Any system using ratchet straps should be able to withstand having at least one of the straps completely fail. And you be able to continue riding at speed without stopping to deal with it.

Regardless of how high quality the straps are or how carefully they are installed, if the fuel tank security would be at risk with just a single strap failure, that is not a good thing. When on the water, strapping failures are more likely in situations where you cannot stop and fix it. Rough water, waves, wind, weather.

This past summer (or last summer) a Bimini rider lost their entire rack when it broke loose in difficult conditions. So you really, really do not want a strap system than has even a possibility of failing should any of the straps loosen, fray, unlatch, or jerk the linking hardware apart.



Hooks like this, two across the back and two on each side under the rub rails, seems like a good starting point.

[4-keeps]

Good luck! I personally don’t see how a racks weight is any real concern over dealing with possibly losing or having the 12 gallon tank possibly ripped off the ski if the conditions became bad enough. Plus the inconvenience if you have others in the group which I’m sure you do, having to deal with the issue at hand. I wouldn’t think that rack by itself wouldnt weight anymore then 10-15lbs. Best regards Keeep us posted either way once you have a game plan.

Billy D

[K447]

The main concern with racks is where they concentrate the load weight into the rear deck, and how well the mounting is able to resist twisting and harsh hull motions in rough water.

The rear deck material is close to flat and not all that thick. Concentrated load areas can flex the deck material and lead to stress cracking. Since it is under the traction mat it might not be noticeable until the deck was seriously damaged.

The linked rack appears to use a pair of round bars to support the rack on the deck. Unclear how much loading concentration might occur.




I would like like to hear how this rather large fuel load has faired in real world conditions.

[4-keeps]

The racks have fair excellent that’s why I posted the link on the RT racks. I owe one now for Gina’s Kawi and have friends with them that have made the crossings more then once using the RT rack. You can’t take crossing the gulfstream lightly. We have been in 10+ footers out there, I’m personally not playing with a 12 gallon tank sitting flush with straps, webbing, whatever concoction to hope for the best. Not worth putting yourself or others at risk.

[Joeyman15]

When we went to Bimini and had few guys with a rack. It was super rough and one of the racks ended up punching a hole through back deck of one of the skis. His ski completely filled with water and had to be towed. I would make sure you spread out the load if use a rack. Honestly after that I won't use one in open water.

[Saum700p]

6-7 gallon internal using the removable rear bucket as a template seems to be the best option, imo. Having two made as we speak. Any quality welder shouldn't have a problem using the plans and pictures from around here.

Billy D, let me know the next time you'll cross. I'll make that run with you'll.

[4-keeps]

6-7 gallon internal using the removable rear bucket as a template seems to be the best option, imo. Having two made as we speak. Any quality welder shouldn't have a problem using the plans and pictures from around here.

Billy D, let me know the next time you'll cross. I'll make that run with you'll.

Sure will Bill!

[4-keeps]

When we went to Bimini and had few guys with a rack. It was super rough and one of the racks ended up punching a hole through back deck of one of the skis. His ski completely filled with water and had to be towed. I would make sure you spread out the load if use a rack. Honestly after that I won't use one in open water.

Yeah Joey the RT racks or totally different then the ones your probably referring to with the four legs for support. I own one of those as well, with that being said I used heavy duty 6ÔÇØ-8ÔÇØ rubber/cork pads underneath the existing legs with rubber feet the first year crossing. The second and third time crossing I have the four legs customized with 6ÔÇØ SS flat bar and epoxy rubber/cork pads to the bottom to help distribute weight and making sure I would lose the pads from underneath. With that being said I knew the potential problems in its design from others having the same issues you mention above.

Billy D

[KEYZBUM]

I know you said you didnt want a rack But if ya do ..

https://pwcsuperrack.com/

[2fast4u]

with 12 extra gallons that is a total of 30.5 gal. a 200 mile trip is pushing your max fuel mileage . if you can get 6.55 mpg for the entire trip you would be out by the time you get there. Even the best pwc running 35 to 40 mph in calm water can hardly get 7 mpg. be sure you have a support boat with extra fuel just incase the water conditions cause you to get less mpg than you caculate .