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  1. #1

    just bought a 947 engine with custom work done need help

    i bought a 947 with miller heads and some kind of carbon fiber reeds and 2 unknown mikuni carbs. ive ran ito many problems that other seadooforums seem to ignore and not help me out wth. so ive signed up here in hope for some help. i was replacing the starter and notice there was a brass hose fitting behind it along with the 2 on the other size of the crankcase the 2 that come on there from the factory are hooked up to the carbs. 1 for each "pulse" on the carbs. is this ok to have them both hooked up to the carbs since im using premix and dont have an oil pump? and what would the extra one behind the starter be for?


  2. #2
    KrunchovXPL-GTX-RX's Avatar
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    Of the two fittings behind the starter that come from the factory one is for the pulse fitting on the front carb (stock carbs only have one fuel pump on the front carb) and the other goes into a one way check valve that provides pressure (rather than the push me/pull me pulse for the fuel pump) to the RAVE solonoid.

    Now the "extra fitting" I am not sure about. Could you describe the size and location a little more clearly? By your description of on the "other side of the cases" from the pulse/RAVE supply fittings it sounds like you are looking at the case water drain fitting.

    The oil pump has nothing at all to do with the carbs. If those are some kind of aftermarket carbs with a fuel pump on each carb then they would indeed need two pulse hoses and if you are running the RAVE solonoid then you would need another pressure supply fitting for it (with check valve and such).

    If the RAVE housings have been drilled out so that it is running 787 style then you do not need that solonoid or the hose or fitting.

  3. #3
    first of all. thanks alot for a quick response and your help.
    i have two 947's one is stock and needs alot of tlc and the other is the one i'm putting in. the stock one has the two hose fittings your describing. one for the carb and one that wraps around to the 3 way for the rave valves?
    the one i'm dealing with has those two and another. the only way to see the other one is to remove the starter. it has aftermarket carbs both have "pulse" on them meaning both have fuel pumps. correct? so that is the reason for the extra fitting? one for each carb and one for the rave's?

  4. #4
    just another problem i ran into. the carbs are upside down. after flipping the carbs the right way i realized the guy flipped them because the exhaust was in the way of the bracket connecting to two throttles. is there something special about these mikuni carbs(their not the factory ones) that they dont have to be the right way for the float to... float.

  5. #5

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    Cool

    these carbs will operate in any position

    cd

  6. #6
    KrunchovXPL-GTX-RX's Avatar
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    There is no float. These machines use a diaphram that works off the intake pulse through the carbs. The pressure (or lack of pressure as in vacuum) difference between the throat of the carb and the ambient outside pressure pulls the diaphram down onto the pivot arm thus opening the needle as needed. If you look on the diaphram side of the carb (on a stock 947 set up it is rear facing plate) you will see a small hole. This allows for the pressure actuation of the diaphram.

    That said, can you take a pic of these carbs you have? Also, on stock 947 carbs the throttle plates (where the cable and the synch bar connect to the throttle shaft) should be on the bottom as mounted (facing away from the pipe). In a normal mounting, the exhaust could never be in the way of the throttle linkage.

    The purpose of the pulse line to the fuel pump is that the pump also works via a diaphram. The push/pull of primary compression/intake vacuum in the rear case works on a diaphram inside the fuel pump. Two check valves in the pump keep the fuel going the way it is supposed to go.

    If I can see these carbs I can tell you if they each have a pump as one with looks a lot different than one without.

  7. #7
    thanks for all the help! yes they do both have fuel pumps. both have that fat rectangle on the side labeled with a down arrow "pulse" and an up arrow. the carbs are very simple, no choke and they dont have a mounting plate they mount inside of a rubber tube with a clamp on the outside. and they have individual air filters. ill get pictures as son as i can.
    ok so they can be mounted upside down. aweosme
    now my throttle cable is too short because the factory carbs had the throttle cable plate on the front(mag) now its on the back do i have to make one? or are there some out there for this specific type of application?
    also the engine came with miller tse heads and one of the domes has alot of chunks out of the top (the pistons ,rings, and walls are fine so i assume he rebuilt it with the scarred domes) where do i buy more domes? the ones i have are 44ccs what do you guys recommend?
    i can't thank ya'll enough for all of the info. i'm knocking out all of these problems left and right.

  8. #8
    KrunchovXPL-GTX-RX's Avatar
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    Those are spigot mount carbs. I have not messed with too many of the aftermarket carbs but maybe one of the speed demons will chime in on this.

    Can you tell what size the bore is? This thing may not be a 947 anymore.

    As far as the domes, I think 44cc domes need race fuel. For pump gas you probably want to be up around 48 (or whatever Miller has in that size range).

    What year electronics are you planning on running it with? With a '98 MPEM you just need a throttle cable that will reach. If you have a '99+ MPEM you need the TPS and you may have a problem.

  9. #9
    its def. a 947 it says it on the plate. this engine says 00 and the blown one i took out says 98. the seadoo is a 98 and i assume the engine i'm putting in is a 2000 i need different electronics? what do i do about the throttle cable beign too short?

  10. #10
    KrunchovXPL-GTX-RX's Avatar
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    The tag just tells you that it started life out as a 947 (88mm bore). The PO could have had it turned into a Big Bore 1050 (a popular mod for the speed slaves out there). If it has been overbored, you need to know this for setup purposes (and maybe to get the right domes).

    If the boat is a '98 and the engine is a 2000 then you will need a mag cup off a '98 (the only difference in electronics is the mag cup). In that case you will just need to find a throttle cable long enough since the '98s did not use a TPS on the cable like the '99+ did. If the mag cup has two little magnets and one big one it is a '98 style. The '99+ had three small magnets and one big one.

    You may even have to get a cable custom made. There is a guy that goes by dsolie on here. He might be able to point you in the right direction.

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