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Discussion Starter #1
Before I mount the tanks and drill the fuel fill holes, does anyone have any input on location?

17'10" Sanger. 410 sprintcar motor on alcohol. Estimated hp 650.

Rear motor plate is 35 1/2" from the transom to the front of the rear motor plate. Shaft angle is 8 1/2 degrees. Let me know if I need to provide more info. Not racing it, but would like to get 80+ mph.

Thanks
 

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Drill for much larger fittings than you think you'll need and install shut off valves (approved for your specific type of fuel) at the tanks.

Leave enough room between the transom and the tank to service the cav hardware. Beyond that, let the flattie guys chime in about specific placement.
 

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Discussion Starter #4
Thanks VDR.

Curious when some of these Flatty guys are gonna appear????
:wtf:
 

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Don't want to leave you hangin...
Most Saddle Tanks in Flatbottoms are mounted where it makes the most sense in relation to the fuel fills. The picture below shows the fuel fill in the "standard" location...just behind where the cap turns inward toward the gunwale.
You say that you need to drill holes for the fills...if you have already filled them and want to do something trick....you can weld tubing to the tank and have the filler on the inside of the boat...works really well and you won't have to drill through the boat to mount the fills. The thu-hulls tend to move a bit and fracture out from the bolt holes...seen alot of nice paint messed up by the fills. If you decide to go through the boat with the fills..at least make a thin neoprene gasket to install under the fills or make a gasket out of clear silicone by spreadin a thin coat on the bottom of the fill and let it dry before installing. Oh..and don't go too heavy with the hose between the tank and filler...makes the fills too rigid which leads to the fractures from the bolt holes...think radiator hose type flexibility.
Also, CP Marine sells a real nice flush mount filler...they're pretty proud of them, but work and looks pretty good too.

1-1/2", 2" and 3" Billet Cam-Lock 1/4 Turn Fuel Fills - CP Performance

 

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Most I've encountered are roughly placed 12" to 20" off the inside of the transom..... I would also agree with Sammons post on locating the fuel fills. I saw in some poor pictures my current boat looks to be much more forward, maybe 30" off the back. I'll try and measure it tomorrow, Todd~
 

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Took a measurement, the current flats tank is 31" off the back of the transom. Thats just where it landed to line up with the existing fuel fill. Having camera troubles, can't take photo's today. Tried posting some fuel fill pic's last night, but the website was giving me fit's. Lets see if it will work now......
 

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Discussion Starter #9
Thanks Guys,

gotta a PM from Sanger448 sayin 27" from transom. I'm reading everything from 35" to 12".

:)st Decisions, decisions.

F1 thanks, when you get time, it would be apreciated.
 

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Discussion Starter #10
Dave,
How important will the balance be? Thanks for the insight on the "gasket idea" I hadn't though about fracturing.
 

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Based on the fact that alot of old flats I've seen have a tendency to hop, I think I would mount them as far forward as possible. You can only go so far, you are ultimatley limited by where you can place the fills. Take a close look of the photo I posted looking into my black boat. Notice the fuel fill in the corner. It can't go any further forward, it runs out of flat real estate. Put your fills as far forward as your comfortable with, and let the tanks fall where they may. Just my worthless opinion. Good luck with the project, Todd~
 

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Dave,
How important will the balance be? Thanks for the insight on the "gasket idea" I hadn't though about fracturing.
With your engine at 35 1/2 inches off the transom(depending on where the strut is mounted), you will have no "hop" issues at 80-85mph.
Put the fuel fills where they look best on the boat(where it is flat), and as Factory1 says let the tanks fall where they may...
Set the plates flat off the bottom, leave your foot in the down(hopefully it has a downpedal) till the horsepower sets the boat, get off it and you'll be good(maybe with a tweak or 2 on the plates).:happy::happy:
 

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Dave,
How important will the balance be? Thanks for the insight on the "gasket idea" I hadn't though about fracturing.
After repairing all the cracks around my fuel fills I tried several things to keep the cracks from reappearing. Like Dave suggests I made some rubber gaskets for top and bottom to sandwich the fiberglass between the fill and a tapped 1/8 inch backer plate I made for the screws to thread into instead of nuts and washers. I drilled the holes in the hull slightly larger to allow for movement and I used a 3 inch piece of the soft silicone rubber they use for turbo couplings instead of the the radiator type hose. So far so good. Also I filled the holes that went thru the hull for the tank straps and made some nice blocks of hardwood with counter suck bolts sticking up to go thru the straps. I sealed them with resin and glued them to the bottom with a polyurethane construction adhesive by loctite called PL Premium. Home depot or dixieline sells it.
 

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Discussion Starter #14
Great advise, guys. I have the back of the strut barrel 23 1/4" from the back of the plates with 8 1/4" plate length. Any thoughts?
 

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Good info as usual and the timing is perfect:))THumbsUp..... just getting ready to install my tanks, any suggestions on vent type and location?
 

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Good info as usual and the timing is perfect:))THumbsUp..... just getting ready to install my tanks, any suggestions on vent type and location?
Any boats I've had with vents are good for one thing, spitting fuel out onto the paintjob. I prefer vented fuel fills, no auxiliary vents, but thats just my experiance.
 
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