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Message |
    
rick jacobs
Member
Username: rickster
Post Number: 11
Registered: 06-2007
| | Posted on Friday, July 17, 2009 - 10:05 pm: | 
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1990 200 merc. there are 3 carbs, seating in boat looking into carbs i see jets .096 these jets are located near the top of each carb. top carb has one jet in left side hole and no jet at right side?? middle carb has 2 jets and bottom carb has jet in left hole. is this normal looks like im missing 2 jets? Had a mech. rebuild carbs but stalls at idle runs great at hi speed... HELP PLEASE |
JB
Senior Member
Username: beckerjs
Post Number: 1772
Registered: 11-2005
| | Posted on Saturday, July 18, 2009 - 09:05 am: |
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here is the exploded view for your carb, It doesn't say what jet goes where but does say how many jets are there, you need a manual
http://www.crowleymarine.com/mercury_parts/520/110.cfm |
Graham Lamb
Senior Member
Username: galamb
Post Number: 5681
Registered: 05-2007
| | Posted on Saturday, July 18, 2009 - 10:47 am: |
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Yes, you definately need the service manual for your particular motor (sorry, I don't have it or would post the diagrams for you).
Here's a "similar" carb to yours - the 200 horse models that followed yours did not use a backdraft jet (marked B on the diagram), so those (holes) should be empty.
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Graham Lamb
Senior Member
Username: galamb
Post Number: 5682
Registered: 05-2007
| | Posted on Saturday, July 18, 2009 - 10:57 am: |
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After digging a little more, there is no rule of thumb for the backdraft jets.
Can you see a casting number on your carbs? Should be a WMH or WMV followed by a digit or two.
Merc used about 40 different models of carbs on their V6 powerheads between 1990-2000 and the jet sizes seemed to change with every new number.
If you can find the casting numbers I may be able to give you what jets should be in what carb - and you can confirm that you are not running "unmatched" carbs - they should all belong to the same (family) or that could cause you problems as well.
For example, if you have 3 WMH-3 carbs, you can swap them for WMH-16's, but you have to change all 3, can't just do one or two... |
rick jacobs
Member
Username: rickster
Post Number: 12
Registered: 06-2007
| | Posted on Saturday, July 18, 2009 - 04:08 pm: |
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Graham, Thanks for all your expertise! this helps BIG TIME Thanks again. |
rick jacobs
Member
Username: rickster
Post Number: 13
Registered: 06-2007
| | Posted on Saturday, July 18, 2009 - 06:01 pm: |
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Graham, top carb #46-11519 this one has missing backdraft vent jet. middle carb #46-21539 this one has both idle and backdraft jets. bottom carb #46-31529 this one has missing backdraft jet. What do u thing could this be the problem of no idle?? |
Graham Lamb
Senior Member
Username: galamb
Post Number: 5703
Registered: 05-2007
| | Posted on Saturday, July 18, 2009 - 06:46 pm: |
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Those are a matched set of WMH-3's, should all have backdraft jets.
The backdraft jets won't affect the idle. They are there to improve mid-range fuel economy by lowering the air pressure in the carb - (since these reduce the pressure in the carb bowl to less than the outside air pressure, less fuel is forced from the carb(leans out the mixture)).
These carbs can be a major pain to set up if they have been rebuilt, cleaned or otherwise fiddled with - without a service manual turned to the correct page from the point when they are pulled - there is stuff you need to note/record and other things you shouldn't fiddle with.
On the idle side of things, the 6 fuel mixture screws need to be adjusted identically.
Additionally, the air trim screws were factory set. If they were removed for cleaning and the number of turns from "seated" was not recorded for each of them, the carbs will forever be out of balance (unless tediously played with to get them set back up).
The service manual contains over 40 pages dedicated to setting up these carbs. "Balance" is the theme through most of it. Each cylinder is fed independantly cross wise (so the left half of the carb (pair) feeds the right cylinder in that pair) and all 6 must be completely synchronized or it don't run right.
Here's the jet specs...
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rick jacobs
Member
Username: rickster
Post Number: 14
Registered: 06-2007
| | Posted on Saturday, July 18, 2009 - 07:39 pm: |
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Wow this is some info i will need to p/u a manual, i had a marine mech go through them i will need to double check his work. Thanks again |
rick jacobs
Member
Username: rickster
Post Number: 15
Registered: 06-2007
| | Posted on Saturday, July 18, 2009 - 08:41 pm: |
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Graham, i pulled out air idle jet and it's a .096 wrong one? |
Graham Lamb
Senior Member
Username: galamb
Post Number: 5707
Registered: 05-2007
| | Posted on Saturday, July 18, 2009 - 08:52 pm: |
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.096 is a backdraft jet, for a WMH-21 carb (later model 200 horse)
Sounds like the guy who did your carbs didn't read the manual very well... |
