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Old 10-21-2019, 01:23 AM   #1
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Default Carbs

I have 5.7 merc with alpha 2 outdrives and carbs can anyone advise me on the jetting for the carbs my port engine appears to be running very rich with unburnt fuel being emitted any suggestions greatly appreciated thanks
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Old 10-21-2019, 02:14 AM   #2
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2 or 4 bbl? If the starboard engine is running ok the port should be jetted the same. Are you sure itís a jetting issue and not something else wrong with the carb?
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Old 10-21-2019, 02:22 AM   #3
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2 barrel both run really well thats what i cant understand the person i bought the boat from said that he had both carbs rebuilt run great but port smokes a lot (black) with unburnt fuel do u have any thoughts on cause or what i should be exploring thanks again
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Old 10-21-2019, 02:23 AM   #4
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Any suggestions to explore will be appreciated
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Old 10-21-2019, 02:27 AM   #5
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I'd first recommend that you download manual #24 from documents section. Some good info on carburetor checks and jet sizes. Also see page 1C-10 for causes of rich conditions.
You may be getting too much fuel, or, too little air.
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Old 10-21-2019, 02:29 AM   #6
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I will check that out thanks
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Old 10-21-2019, 12:30 PM   #7
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Quote:
Originally Posted by jrsick View Post
I'd first recommend that you download manual #24 from documents section. Some good info on carburetor checks and jet sizes. Also see page 1C-10 for causes of rich conditions.
You may be getting too much fuel, or, too little air.
Yup jr has got you covered on this. First thing to look at is the choke to verify its opening.
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Old 10-21-2019, 12:33 PM   #8
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I had a rich condition like this with my Mercarb 2bbl

Turns out I had a bad float which wasn't regulating the fuel into the bowl properly and excess was dribbling into the carb from the vent.

This was after a rebuild and changing to the brass floats. Turns out it had a pinhole in it. Improper setting of the float levels would also do this.

Found this by taking off the spark arrestor and with engine idling, looking down the carb throat. Saw fuel bubbling out the vent tube.

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Old 10-25-2019, 12:12 AM   #9
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The jets are non adjustable. Are you referring to the needle valves? if you are the needles should be turned in all the way ( do not overtighten) until it seats and then turned back out 1 and 1/4 turns. These will adjust the air mixture which will resolve rich burning fuel . Make sure the choke is opening all the way. And yes what john said about the float.
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