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  1. #1

    putting sl780 back together (custom build)

    newbie to the forum, well atleast posting, been reading all sorts of info to forum on this build im doing.

    basically i bought a 1996 sl780 and took a saws all to it, cut engine and pump housing out, and am going to bolt it to a john boat to create a "jet jon". the engine was a mess, but i have replaced the mag piston (ran lean like they are known for) rebuilt all carbs, replaced exhaust manifold and expansion chamber, replaced crank seals, pump bearings seals, and luckily cdi and electrical box is in IMMACULATE condition. now the next step is putting it all back together, the main questions i have is about fuel return lines (i will not be using original tank) and then re plumbing cooling hoses (simply cant remember how they go, and made mistake of not taking pictures, got over eager on the build. so any info on fuel lines would be awesome, i assume the fitting on carns with the TINY hole is the return line? as a built in pressure fitting?


  2. #2
    ripcuda's Avatar
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    Welcome to Green Hulk!

    Sounds like a cool conversion project. I love the little jet boats. Is your boat fiberglass where you can graft in the cut ski hull?

    I'm curious... what was wrong with the exhaust manifold and pipe that warranted a replacement? Those always seemed so indestructible to me.

    Fuel routing is pretty simple and you can simplify it even more on your boat. There are 2 supply lines: main and reserve. The reserve line sticks down lower in the tank. Both of these supply lines feed into a fuel selector valve... 2 lines in... 1 line out (based on switch selection). The single supply line then goes through a fuel water separator (jar looking thing) then to the fuel pump (triple outlet pentagon pump in your case). From the fuel pump are 3 "outs", one for each carb, an "in" to connect the single supply line to, and a pulse to connect to the pulse fitting on the engine crankcase (below intake)... this pulse line powers the fuel pump. The 3 carbs are linked (daisy-chained) together for the return fuel line. The single return fuel line then goes back and dumps into the fuel tank.

    If you have an easy way to gauge fuel levels... you could do away with the reserve fuel line and change the fuel selector valve to a simple on/off fuel shutoff valve.

    Show us some pictures of your build.

    Cheers!

  3. #3
    ripcuda's Avatar
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    Hmm... looks like maybe your '96 SL780... didn't have a reserve line after all... cool... as simple as it gets.

    Click image for larger version. 

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    Cheers!

  4. #4
    ya ill be using a completely different tank and want to see if its possible to only have a line to the pump, and then a return line. i wont be using the polaris send unit at all. i think i have the fuel lines more figured out than i do the water lines, thats the part i paid the least attention to when taking engine apart, and as far as the boat its a 12ft aluminum (its the second aluminum one ive done) i try to stay away from fiberglass as much as possible.

  5. #5
    ripcuda's Avatar
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    water lines for 780

    Click image for larger version. 

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    Cheers!

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