carb rebuild question

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scott68

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1984 johnson 70 been having problems since i got it, tries to stall when giving throttle from start, push key in and it goes fine from there, this only happens from the start. i have rebuilt all and problem hasn't gone away. when under load if i shoot pre-mix into middle carb, it clears and goes. so i took the carb off today to check and there was a brass plug on the top left rear of the carb i wasn't able to get off at last rebuild so i thought the problem may lie there. with a little heat i was able to get it off and get to the jet and remove. it seemed clear but cleaned out well anyway.now here is the problem... this jet and the low speed jet are 2 different sizes and didn't check this first when i took them out, which is which and now i'll go back and check the rest to make sure they are in the correct spots. sorry for the long post but i can't find a diagram of the carb anywhere. thanks in advance
 
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scott68

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Re: carb rebuild question

thanks TD, got it. can the link and sync be done effectively without a tach as my boat wasn't equipped with one. i also borrowed a timing light
 
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scott68

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Re: carb rebuild question

Rig a spark tester and have the gap set to 7/16". Hook up the timing light to the #1 plug wire. Crank the engine over and set the spark advance to 4? less than what the engine calls for.


is a spark tester a necessary part of this and do i need to have it on all 3 wires. if so, where can i pick 1 of these up??
 
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scott68

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Re: carb rebuild question

well I pulled the carb, cleaned and put back on, checked spark with a checker, jumped the gap and was crisp and bright, set timing, it is listed in the manual for 18-20 and was at about 14, but still the same bog at 3/4 throttle till key is pushed. i can deal with it, still runs good except for this small issue and i just want to fix it, any other ideas to look into. i would like to thank everyone on this site that has given any input on any problems as i haven't yet had an issue that wasn't resolved here.
 
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scott68

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Re: carb rebuild question

i did the timing right at the dock, after engine was warmed i checked and adjusted as it was retarded about 3-4 degrees, will be taking it out monday to see how it responds as it still seemed to bog down and to see if it starts a little easier. is there something else i should be looking for
 
tashasdaddy

tashasdaddy

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Re: carb rebuild question

you need to make sure you have spark on all 3, and i would check your compression. when it starts to bog, have someone pump the bulb in the fuel line from tank, if it picks up, it is fuel delivery related.
 
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scott68

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Re: carb rebuild question

checked all 3 wires and have good, even spark. the compression is 90-95, i know it's a fuel problem, just can't figure out where. when it bogs i sprayed pre mix into carbs, top and bottom made it bog more and middle made it clear and pick up, and that is the one i just had off.
 
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scott68

Seaman
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Messages
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Re: carb rebuild question

hey TD, any other ideas, got back down to it today, put a new fuel line from tanks to motor and then squeezed the bulb while it was bogging and no change at all, and the bulb was very firm. again push key in and it clears, what about a rebuild on the fuel pump or is that a waste of time. now i'm really stumped
 
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