Backfire/misfire thru carb

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  • fleetwin

    US Member - 2 Years
    Replies: 4061
    Topics: 41
    #212500

    OK, so you have the “OMC Turbo jet”. First, I’m pretty sure that this unit has a fairly high idle speed to make sure it pumps enough water to cool the engine. And yes, it will be tough to look inside the carb throats to ensure both butterflies are closing fully.
    So, like I said before, try moving the cam roller away from the cam slightly at idle speed..
    Try disconnecting the link between the two butterflies, this should ensure both are closing fully provided the roller is not touching the cam….And yes, it is possible that one of the carbs has some sort of binding issue/wear causing its butterfly to stick open slightly, but this is not that likely.
    Let me know if either of these steps clears up the idle, we can go from there with the syncronization….


    Beno


    Replies: 78
    Topics: 26
    #212691

    Ok heres what I’m dealing with.. I think the black is just sealant.
    upon closer inspection it looks that both butterfly’s are closed at the lowest setting.

    Attachments:

    fleetwin

    US Member - 2 Years
    Replies: 4061
    Topics: 41
    #212697

    OK, well I don’t want to be a “downer”, but looks like some pretty shoddy work has been done in the past… A few things of concern in your last picture:
    That idle speed screw is cranked all the way in….This usually indicates idle issues that could only be dealt with by cranking up the idle speed
    The plastic threaded link is upside down on the throttle cam, the engine will never work correctly this way…

    I hope you didn’t pay too much for this, any chance of returning it? What happened to the original powerhead?


    Beno


    Replies: 78
    Topics: 26
    #212698

    more pics

    Otherwise I have them all uploaded at
    https://link.shutterfly.com/kDOEeP8xg9

    Attachments:

    Beno


    Replies: 78
    Topics: 26
    #212705

    interesting.. I didn’t notice that plastic linkage reversal.. I’ll get it fixed, but I think that would just be a position thing.

    the original 115 had a cylinder turn into a meatball about 12 years ago. I sold the long block to a guy who was going to rebuild it in lake champlain.
    couple years later I found this 140hp bubbleback on a electric transom, the lower unit had self destructed.
    The seller said the powerhead had been bored .30 over and was “a good runner”.

    I accidentally had the throttle up on start once and it revvs up very impressively… it’s just not happy at Idle.

    I dropped the powerhead on the LDrive and put it in storage, been there ever since.

    I’ve been selling online all year and with all this government molesting the economy with all their inflation/stimulus and PUA/jacked up unemployment I’ve been selling stuff like CRAZY. So I pulled this jetboat out and trying to get it sold.


    fleetwin

    US Member - 2 Years
    Replies: 4061
    Topics: 41
    #212759

    Well, all you can do is get this powerhead syncronized properly and try again. Pull the carbs apart and inspect the low speed jets if problems persist after proper syncronization. The pictures you posted look as though the butterflies are closed. But, don’t forget to disconnect the link between the two carbs and retest, just in case the linkage is preloaded open.

    You still have the carbs from the damaged powerhead, perhaps you could try those as well. Keep in mind that the jet drive and conventional outboard are completely different animals, the original carbs are probably jetted much differently for this application. The one big difference between the carbs is that the old 140 uses a conventional choke, the newer jet drive uses the electric primer. So, you will have to transfer the primer valve and plumbing over also. The carb to intake gaskets are different also, the older gaskets don’t have a hole for the primer hose to spray…

    You can’t tell much by revving the engine up in neutral, even though this jet drive doesn’t really have a neutral. And yes, the position of the throttle cam linkage will make a difference….
    Good luck, sure hope I am wrong about that older powerhead. Don’t forget to do a compression test…


    Beno


    Replies: 78
    Topics: 26
    #212764

    Ok. I went up and checked into it. The good news is i checked the compression. 128,128,123,122

    I realized the trigger plate was siezed.. the connecting linkage came off as i investigated. I put some pliers on the exposed part and started working it. I must have moved it 2000-4000 times and hit it with pB blaster. Its not usable yet but its a lot better.. i advanced the plate just a bit and the idle cleaned right up. So thats the good news.

    I pulled the cooling water supply hose ans poured some water down it and blew it to pressurize it a bit.. water started coming out under the engine. The exhaust adapter plate is likely frost damaged. Uggh. Ill have to pull the engine and inspect.
    Water also came out under the bubbleback… not good.


    Beno


    Replies: 78
    Topics: 26
    #212767

    See number #30 .. water gets in the bottom and someone puts it away for the winter without getting it out…

    3ZQdbNwI

    • This reply was modified 1 year, 1 month ago by Beno.
    • This reply was modified 1 year, 1 month ago by Beno.
    Attachments:

    Beno


    Replies: 78
    Topics: 26
    #212768

    So at this point the questions are now.. how can I free up the Trigger/Ignition plate without removing the flywheel? Can I spray PB Blaster down the flywheel puller holes without damaging anything?

    and If I have to pull the flywheel what is the correct re-torque ft lb number (and how on earth do you hold the flywheel while torquing?)

    • This reply was modified 1 year, 1 month ago by Beno.
    • This reply was modified 1 year, 1 month ago by Beno.
    • This reply was modified 1 year, 1 month ago by Beno.

    fleetwin

    US Member - 2 Years
    Replies: 4061
    Topics: 41
    #212802

    OK, well a jammed mag plate will certainly affect sync and running for sure. The sensor/trigger assembly has two different bushing surfaces. One is the pilot bushing on the inside diameter of the upper bearing assembly. I guess it would be possible to spray WD40/PB blaster through one of those puller holes, it will probably make its way down to the pilot bushing. The other surface is the plastic bushing that rides on the outer diameter of the assembly and sits down on top of the outside of the upper bearing assembly. You can see what appears to be a white plastic washer between the sensor assembly and upper bearing. You can try spraying the WD40 around where the plastic bushing is, it might work its way inside. It will be difficult to see this on your turbo jet.
    To remove this flywheel, you will need the OMC puller assembly, don’t attempt it with a substitute puller. A big impact gun will remove the flywheel nut, and can be used on the big center puller screw for flywheel removal. Reinstallation will require a big torque wrench and a ring gear holder tool to secure the flywheel while using the torque wrench. Will get back to you with the torque spec.. Unfortunately, sounds like someone left water in this unit during the winter and popped the adapter open….What a mess.
    I should have asked how you were running the engine prior to now, seems like you were running it with no water…Won’t hurt anything on this unit, there is no rubber impeller. But, running the unit out of water reduces back pressure and could cause the unit to run lean/sneeze at idle. Maybe a good welder can patch up the cracks…Unfortunately, these turbo jet units were not OMC’s finest hour….


    Beno


    Replies: 78
    Topics: 26
    #212807

    Ok I will try the penetrating oil.. personally I’d rather work that trigger for hours than pull the flywheel, I’ve done it in the past and it creates such a issue. usually they just WILL NOT release. also the weird plastic thingie that hooks the linkage to the trigger plate (timing linkage?) is weirdly loose and doesn’t hold the linkage very well, any pressure and it falls down and out .. is that normal? circled:
    linkage

    otherwise I will pull the motor, I have one mystery water leak near this thermostat assembly under the motor shown in the attached picture of a similar motor.
    thermo
    my question is.. does the thermostat (when hot) allow water to “A” Drain down from the cylinder jackets, or to “B” travel up into the cylinder jackets… the only thing that makes sense to me is “A”.

    Attachments:

    Beno


    Replies: 78
    Topics: 26
    #212832

    Here is a pic of someone elses exhaust plate after its fixed .. problem is common

    a518531424945bdb6ec05156405771481

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

    US Member - 2 Years
    Replies: 4061
    Topics: 41
    #212833

    OK, well those white plastic connectors are fairly flimsy even when in good shape. But, this one has probably been worn out trying to move that jammed mag plate, I would definitely replace the ball/socket assembly.
    The water flows out of the cylinders down through the hoses to the thermostats. So, is this the only leak you have?? If so, perhaps the big adapter is not freeze damaged. Perhaps one of the hoses is leaking, or one of the thermostat cover gaskets is NG. This set up is a pain in the butt at best, but near impossible to service with the bubble back exhaust. I have spent many hours trying to wrestle the little springs/seals back together while the powerhead was in place. In the end, it probably would have been easier and taken less time to just pull the powerhead. But, I would try to pinpoint the actual leak prior to pulling the powerhead so you can be sure it is actually fixed after reassembly. The last thing you want is to complete the job only to have the leak persist. I’m not sure if there is some way to run water through the system without running the engine, which might make it less difficult (and safer) to find the actual leak.
    Good luck…


    Beno


    Replies: 78
    Topics: 26
    #212858

    No Two leaks, the major one is below/under and the smaller one below the thermostat plate.

    But You know whats interesting.. is looking at the design of the plates. I should have noticed a crack of this magnitude, That is a huge miss.

    I’ll put the Video scope on it and get you all some pics of the damage thru the scope if I can.

    • This reply was modified 1 year, 1 month ago by Beno.

    fleetwin

    US Member - 2 Years
    Replies: 4061
    Topics: 41
    #212864

    I haven’t had much experience with these things, but it seems like the powerhead and adapter are going to have to come out of there in order to have the cracks repaired… I don’t think you could have seen a crack underneath that exhaust/adapter housing very easily. And, it sounds like the powerhead was shot, so you couldn’t run the unit to check for water leaks. Just hoping you didn’t pay much for this rig….

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