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  1. #1

    750 Engine into 780 Hull?

    Has anyone done this? I have a complete 750 engine (Electric/stator/cdi/etc) that I want to put into my 780 hull that had a catastrophic lower/upper end self destruction.

    Since I have a complete engine w/ electrics out of a 750, is there any other major gotchas with putting it in the 780 hull I should be weary of?

    Thanks in advance!

    -Joe


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Which 780 hull - SL or SLT?
    Which hull did the 750 engine+electrics come from?

    Do you have the 750 exhaust manifold and pipe?
    The 780 manifold uses a different bolt pattern.

    The impeller needs to match the 750 engine power. DO you have a 750 impeller?

    The engine will physically bolt in, and the electrics can be retro-fitted.

  3. #3

    Re: 750 Engine into 780 Hull?

    Not sure which hull the 750 stuff came from.. just got the engine/etc out of it.. I do have the exhaust assembly and have an extra 750 prop for my other 750 that actually works.

    The 780 is an SL Hull.

    I figured as long as I had the 750 stator, cdi, etc all would be good there, was a bit leary on the MFD working with the 780 one, but the pinout seems the same on the electrical schematics.

    One thing I noticed different was a fuel assembly that was mounted in the 780 hull and looks to inject fuel to each cylinder v/s on the 750 it has that mounted to the engine block itself with fewer hoses ... or this might be a vacuum assembly. Didn't really look at it too well yet during my dismantling and such.

    Thanks!

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by jfrelin View Post
    ...was a bit leary on the MFD working with the 780 one, but the pinout seems the same on the electrical schematics.

    One thing I noticed different was a fuel assembly that was mounted in the 780 hull and looks to inject fuel to each cylinder v/s on the 750 it has that mounted to the engine block itself with fewer hoses ... or this might be a vacuum assembly. Didn't really look at it too well yet during my dismantling and such...
    MFD will work just fine. Speedo readings might be slightly off, but they are never accurate anyways

    Sounds like the 780 engine has the triple outlet fuel pump, which is the preferred fuel pump. I suggest you transfer the triple outlet pump to the 750 engine, and adjust the carb hookup. There is a hose diagram posted in the tech section.

  5. #5
    Right on.. thanks for the advice. I'll start futzing with that next then. It indeed is a triple output fuel pump.

    I should be able to use all the hoses/etc for the triple fuel assembly right off the 780 and save purchasing the kit/etc for the 750 I assume? Seems pretty straight forward.

    Thanks

  6. #6
    Actually.. one final question.. can I swap out the carb assembly from the 780 and place it onto the 750? ie: from the reeds on up? the 780 one is much in better shape than the 750. Outside of seals around the reeds? would this work or are they jetted differently?

    Thanks

  7. #7
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by jfrelin View Post
    ...I should be able to use all the hoses... right off the 780...
    Seeing as those hose are more than 10 years old, you should replace all the fuel lines with new. Change the oil lines at the same time.

    Also clean and check the fuel selector valve, as they sometimes start leaking air into the fuel stream when they get old.

    Some Fuji models also have fuel hose inside the fuel tank. If yours does, change them too.

  8. #8
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by jfrelin View Post
    ...can I swap out the carb assembly from the 780 and place it onto the 750? ie: from the reeds on up?

    the 780 one is much in better shape than the 750. Outside of seals around the reeds? would this work or are they jetted differently?...
    The carbs are jetted differently, I believe.

    Have a look in the Service manual, starting on page 100

    You still need to disassemble and clean the carbs, even if they look good on the outside. Internal filters and small passages can get clogged, and will burn down the engine if they are not cleaned before running the engine.

  9. #9
    I reviewed the service manual and they didn't seem to note anything about different jetting between the 750 and 780.

    Any thoughts? If there truly is a difference couldn't I pull the jets from the 750 and place in the 780 carb assembly or purchase new 750 jets?

    Thanks

  10. #10
    Lake Mead Bum & BTLS Mark starflight's Avatar
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    You can swap jets between carbs. The carbs are the same sbn-38s.

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