Backfire/misfire thru carb

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  • billw

    US Member - 2 Years
    Replies: 1592
    Topics: 46
    #244429

    I don’t know anything about Turbo Jets….thank God, apparently….but I can help with the earlier question about the fuel gauge. The back of the gauge should have three wires going to it, most likely black, purple and pink. Black is battery ground. Purple should be key-on positive 12 volts. Pink is the wire that carries the “signal” from the sender in the tank. On the tank sender itself, you should see a pink and a black wire. If they both look black, the pink is probably covered with black mold! Anyway, there is never any 12 volt power at the sender. Do not ever try to apply any either, or you might be meeting your make sooner than you’d hoped. First, check that you have power and ground to the back of the gauge, with the key on. If so, then REMOVE the pink wire from the center of the sender and momentarily ground the pink wire, while observing the gauge. It should go full scale. If it doesn’t, you either have a gauge problem or a boat wiring open circuit. More on that later, if you need it; but that’s usually not the case. If the gauge goes full scale in the previous test, you most likely have a bad sender Make sure the connections on the sender are nice and clean. If it still doesn’t work, measure the ohms across the sender (pink wire is still removed) between the center terminal and the ground terminal. It should be between 33 and 240 ohms, depending on the level in the tank. If you don’t get a reading in this range, the sender itself is bad and will need to be replaced. There are after market senders available (Moeller for one) that can be set up to fit the depth of the tank. You will need to know the depth of the tank in order to buy a sender that will be in the right depth range to adapt to your tank.

    Long live American manufacturing!


    fleetwin

    US Member - 2 Years
    Replies: 4062
    Topics: 41
    #244470

    OK, agreed that the thermostat set up is terrible…You can’t get at the bolts on the conventional outboards, not to mention having them rusted in place…Then trying to get all those pieces/parts/springs/gaskets back installed properly is usually an exercise in frustration….
    There is much more room under the top of the head for those elbows, and it is at the top of the water flow circuit, so this greatly reduces the chance that air will get trapped in the system…If you are going to do anything, I would probably just install the original black turbo jet heads/elbows back on the 140hp powerhead. When you have the heads off, compare the combustion chambers and you will see that the turbo jet heads have much less “squish” resulting in lower compression/longer engine life. There isn’t much meat on the cylinder head water cover for threads, and very little room behind the cover as well. Again, the nature of this jet system is prone to taking in alot of air while bouncing around, so I feel the elbows would constantly be purging air, not just when first started. Be sure to replace the head gaskets if you decide to make this swap.
    As far as the fellow who is emailing you, I’m certainly not saying he is “wrong”. But, obviously the powerhead swap works. The trick will be longevity….These things are subject to harsh use, so they are more likely to have overheat/detonation/preignition issues. Get it buttoned up, and sell it off….


    Beno


    Replies: 78
    Topics: 26
    #244480

    I actually sold the turbojet longblock complete years ago. the heads went with it.. but I’m sure I can get more on Fleabay. I’ll keep an eye out for them on ebay.
    I would need new head bolts and 2 new gaskets if I removed the head right?

    On the fuel gauge that is great info I appreciate it. But what happened is that the gauge was working and for some reason (it’s like a 16 gallon tank) the sensor doesn’t start to read of Empty till you get to 8 gallons.. then it goes up to Full as you get to 16/16 gallons. something new every day.


    fleetwin

    US Member - 2 Years
    Replies: 4062
    Topics: 41
    #244493

    OK, so the original powerhead is gone. I would just order the OEM plastic elbows, remove the existing heads, and drill/tap them for the elbows…. Use new head gaskets, the old head bolts should be fine provided no one has buggered up the hex heads or used excessive heat on them…. Just tell the new owner to use premium fuel, and mix the oil a little heavier than 50:1 recommendation….


    Beno


    Replies: 78
    Topics: 26
    #244494

    as I recall one of the cylinders went Real bad.. so it’s likely only one of the heads would have been salvaged anyway.

    My experience is that permium fuel runs VERY hot.. are you sure the increase in heat is worth the increase in longevity?


    billw

    US Member - 2 Years
    Replies: 1592
    Topics: 46
    #244497

    I actually sold the turbojet longblock complete years ago. the heads went with it.. but I’m sure I can get more on Fleabay. I’ll keep an eye out for them on ebay.
    I would need new head bolts and 2 new gaskets if I removed the head right?

    On the fuel gauge that is great info I appreciate it. But what happened is that the gauge was working and for some reason (it’s like a 16 gallon tank) the sensor doesn’t start to read of Empty till you get to 8 gallons.. then it goes up to Full as you get to 16/16 gallons. something new every day.

    I suppose it could be a very strangely-shaped tank but more likely is that somebody botched a previous attempt at sensor replacement. The senders come to fit a range of say, 6″-12″, 12″ to 24″, whatever. You have to follow a very specific procedure to modify the new sender to fit the tank. If you screw it up, it won’t work right. Like my old boss always said, “Read the destructions!”

    Long live American manufacturing!


    fleetwin

    US Member - 2 Years
    Replies: 4062
    Topics: 41
    #244519

    as I recall one of the cylinders went Real bad.. so it’s likely only one of the heads would have been salvaged anyway.

    My experience is that permium fuel runs VERY hot.. are you sure the increase in heat is worth the increase in longevity?

    Well, I’m not sure it burns hotter, but it does help with uncontrolled combustion which leads to detonation/preignition damage…You could always increase the size of the high speed jets by .002″ to combat any extra heat….But, at this point, now that it is running OK, it is best to just sell it as is….


    Beno


    Replies: 78
    Topics: 26
    #245563

    That omc 140hp is out on tupper lake area this weekend with my brother and the kids.. it does run hot tho! They are stopping every so often to let it cool off.

    IMG9531991

    IMG953198

    • This reply was modified 1 month, 3 weeks ago by Beno.
    • This reply was modified 1 month, 3 weeks ago by Beno.
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    fleetwin

    US Member - 2 Years
    Replies: 4062
    Topics: 41
    #245641

    Perhaps I missed something in one of your posts…But, how is it you are determining that the powerhead is running hot? Are you judging temp based on gage readings? If so, please know that these gages or often inaccurate and are affected by high battery voltage. Did you keep the water cooled regulator/rectifier from the original turbo jet powerhead? Or, are you using the simple rectifier only system that was on the older 140 powerhead? High battery voltage drives those gage readings up giving false readings…


    Beno


    Replies: 78
    Topics: 26
    #245646

    I havent found any turbojet heads yet. So just the stock 1978 omc heads for now

    My brother took the sunbird w/140hp up to Tupper Lake . He just uses a laser temperature shooter to see what temp the block is after pulling the kids around on the tube.

    As far as charging… whatever the 1978 magneto puts out is what we have. All 78 on the block…

    The exhaust system has a lot of rubber hose.. and you can smell its hot.

    See pics

    Josh is good at foul hooking smallmouth bass.

    IMG958257

    IMG_8285

    IMG_8273

    IMG_8263

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    fleetwin

    US Member - 2 Years
    Replies: 4062
    Topics: 41
    #245666

    I wonder if some of the water that is supposed to escape from the top of the heads is directed toward hot spots in the exhaust….Not too familiar with the turbo jet cooling schematic… Have him check temps on top of the heads and on the exhaust manifold/cover on the back of the powerhead…


    Beno


    Replies: 78
    Topics: 26
    #245754

    I think you may be right. We plan on threading some holes if we keep that powerhead in there. Im getting really good at swapping v4 powerheads so we may just put a 115 in next summer instead. Its really got more power than it needs at 140hp (and i think its bored .090 over!)

    Kids are setting new altitide records om their tube.

    IMG_3297001

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    fleetwin

    US Member - 2 Years
    Replies: 4062
    Topics: 41
    #245798

    I would leave it the way it is, but find a turbo jet cooling schematic, the drill/tap the current heads…Do you know where the water from the heads is supposed to be directed? There must be some port somewhere that is plugged off because this is missing….


    Beno


    Replies: 78
    Topics: 26
    #245821

    Yes sir, I do know where it is supposed to go… the two rubber lines merge in a T then go to the Baffle – muffler affair on the starboard rear of the boat… see pic of some boston whaler with turjet.. the pink likes show water flow direction.

    we plan to tap the water jacket covers on the heads.. that way we can just remove the gasket covers and not actually have to go down the whole remove the heads route. new head gaskets..etc.
    the water jacket covers provide the same access to the same waterway path.

    path

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    fleetwin

    US Member - 2 Years
    Replies: 4062
    Topics: 41
    #245847

    Like I said, there is not much room under those water covers for drilling/tapping

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