Fuel tank replacement

[Briguy]

I recently repowered my '78 SeaCraft with Twin 115hp Suzuki 4 strokes. The power package is fuel efficeient and quick.(2.6mpg at 4200rpm 27kts @10 1/2 gph)(38 kt top end)
My problem is the transom is a little heavy. For now, I moved my batteries under the super console and that helped a little. My idea is to drop fuel capacity from about 150 gal to 100 gal thus shortening the tank by about 2 3/4 feet. This would move weight out of the stern and shift the fuel tank center of gravity forward. i am also going to redo my deck scuppers so they rest at the waterline or above. Any thoughts on the success of my idea before I get started?

[Scott]

Capt. Brian Welcome!!

WOW you've got a rather large tank there...Thats almost 9' if I did the math right...And if I did it right you have very little room to shift that tank forward "as is" unless you take the big fish box out in front of the console. I’m not sure on this but I bet your real close to 800-850 lbs for those motors….and about 900 for fuel…. [img]images/icons/shocked.gif[/img]

I have seen boats with this kind of fuel and twin 200's but the boat had a closed transom and bracket..and it sat low in the water.
Just a suggestion...I’m sure your aware that the boat really doesnt sit on a fulcrum or pivot point so shifting weight forward really isnt going to raise the stern of the boat significantly (sure if you put all the weight in the bow to get the transom higher…but then you couldn’t run the thing) It will likely just “squat” the boat in the water more forward….. for that reason I would be somewhat careful on major weight shifting in the boat. (I went through this experiment with weight shift on a much larger boat (38’ sportfish) with a generator/water tank move….and does it change how the boat runs)

If its not on a bracket you might want to look into one with lots of floatation. As far as the fuel tank goes…I would think you would want to reduce the size of it ( For arguments sake...removing 50 gallons = 300lbs weight loss) if nothing more than to get some weight out of the boat…and get the tank under the console….

Curious .. with that kinda weight ,assuming I am close, you must dip pretty low in the stern when you get people back there….hence the scupper change??

Scott

[Trayder]

Hello Briguy-

If you do not need the range your idea is great but for resale and for more range extra fuel is always a bonus. How about installing a water tank up in the bow. It would bring your bow down and give you some fresh water for what ever you may need it for. Unfortunatly it will only add weight to the boat but it should help out your trim issues.

[Briguy]

Trayder,

Thanks for your advice but adding more weight is not what I am after. I had thought about adding a few small bags of shotgun lead in the bow for about 50lbs and that might do it. As far as resale on fuel capacity. I see many i/o& inboard boats on this site with 95 to 120 gallons of fuel. Range? I can go 60 miles off shore, troll all day, come in and still have 30+ gallons in the tank thanks to my 4 strokes. The days of burning 15 to 20gph are over. My previous twin Yam 130's averaged 1.7mpg total. Now I average 3.1 mpg total. No need to carry the extra fuel weight. How tough of a job is removing the console and yanking the fuel tank? I will either have the tank shortened by 2 3/4 feet(from 8+) or just get a new tank? Any suggestions?

[Scott]

Briguy
I would venture a guess that just about everyone on this site has removed or come close to removing the tank....I'm in the middle of replacing the tank right now just have to give them the dimensions of the new tank (old was 100)

The new boats come through with 135...I'm looking to go 120 or there abouts. Removing the console for me was very easy...remove all the screws and it lifts right up (well so to speak)....of course nothing is attached underneath the console on mine either.....

I think I might have a new tank built...they dont cost that much and you would have a new tank....if the old tank isnt that old talk to a tank builder on the feasibility of making yours smaller....depends on how much life you feel you have in the current tank...

Oh yeah my biggest problem getting the tank out was trying to remove the foam inbetween the stringers and the tank.....that was a pain in the neck big time!!!
Scott

[ April 10, 2002, 08:56 PM: Message edited by: Scott ]

[Briguy]

Scott,

Thanks for the imput. Here in Sarasota we are lucky to have so many boatbuilders here. Wellcraft, Chris-Craft, Aquasport, Flats and Bay, Yellowfin... The local marine surplus store has everything and anything for the boater. My old tank is very thick and solid. My raycor filters have NEVER had anything in them. Not even an ounce of water. I am reluctant to buy a new(Marine surplus) tank because they feel so thin. I am going to compare costs and make my decision. Perhaps I will bump up the gallons to 110-120 range.

[hermco]

I think that by shortening the tank and losing 50 gals. of fuel you will remove 350 lbs. of weight from a fully fueled boat (gas @ 7 lbs. per gal.)but also affect the resale value and it might not accomplish what you are looking for,does the boat sit better with an empty tank? [img]images/icons/confused.gif[/img]

[hermco]

The foam is easy just use a handsaw down the sides of the tank and it will "pop" right out.If you decide to replace or resize the tank be sure to epoxy coat before reinstallation it will extend the life of the tank as they corrode from the outside in.

[Scott]

Well hearing about its construction ... your right...I think I too would attempt to use it over the new stuff....I will have to pay extra to get a slightly thicker wall....which isnt that much thicker....

my tank was all corroded due to the foaming in of it...as it was not enclosed in a cavity Like Trayder is doing with the 20. It would have cost me about the same to have the old refurbished..

[capesams]

When I had my new tank made, 105gal.-3/16 thick. mar.grade alum. buy this co. up here. the man told me NOT to foam it in unless I put gluv-it,al-grip,epox. etc. on first. Like mr. h. said.
NO one would touch the old one to do anything to fix it ,they said the alum soaks up the gas because of the pores in the metal.And no matter how long it sat to dry out when you go to weld it could BLOW up in your face. These people would not touch it. This co. has been around a long time, 2nd 3rd gen. so I went with new. $1,000.00