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Any Mercarb Experts

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ayleeuss

Contributing Member
"Hello to everyone. I found th

"Hello to everyone. I found this board and was hoping that someone would be able to answer a few carb questions. Heres the story:
About 2 years ago i bought a '98 4.3 out of a salvage yard. Rebuilt the engine and got it all together (also rebuilt the carb). IT would start right up, accelerate very well and perform well at any speed where the boat was on plane. Thats about 2700 rpm and up. The problem i was having was at speeds above idle like going thru slow speed zones. About 1000 to 1800 rpm. At those speeds the rpm would sometimes fluctuate like i hit the throttle or backed off the throttle. I couldnt seem to figure it out so i took the carb off a 3.0 lx. The motor runs good at all speeds but just seems a little different than the first carb. It doesnt seem to accelerate as fast with the second carb. Even when cruising at 3000 rpm if i wack the throttle it doesnt seem to have the same response as the first carb. IT does run better in the slow speed zones.

1. What is the difference between a 2bbl mercarb off a 1993 3.0l
lx and a 2bbl mercarb off a 98 4.3lx.
2. Any idea why i cant get the one from the 4.3 to work properly in the low rpm's?

thanks in advance to whoever would like to take a stab at this one."
 
"A carb designed to meter fuel

"A carb designed to meter fuel and air for only three liters is likely starving a 4.3 during acceleration, and probably throughout the entire speed range. But it would be more noticeable during acceleration.

The irregular engine control you experienced at low speeds using the earlier carb is most likely due to off target adjustments."
 
"Sounds like float level wrong

"Sounds like float level wrong.
When running rough, is it smoking at all? This would suggest rich mixture/float level too high.
Did you follow the recommended float level when you rebuilt it?
Is the choke fully open when warmed up?
Is your fuel and filters clean?

Rod"
 
"Thanks for the replys guys. F

"Thanks for the replys guys. Float level was checked and re-checked. I have the manual from mercury for the specs. The needle and seat was changed to the new style. Fuel tank was pumped out and fresh fuel added before i ran it. Filter was new, and is still on there running with the second carb.
It didnt really run rough, it would just decrease rpm from like 1800 down to 1500 and stay there. Or it would increase rpm a few hundred. Almost acted as if it was slack in the throttle cable.
I would really like to know what the difference is between the two carbs. Could i just change a main jet and have the right carb for a v6?"
 
Check the carb ID numbers on t

Check the carb ID numbers on the tags and the carbs. I doubt the 4 banger carb is set up for a V-6. The numbers will tell you what carbs you have. Then call Merc. tech. service to get an answer.
 
"Jets are different, depending

"Jets are different, depending on the model of the carb.

Check the table on the last page.<center><table border=1><tr><td>http://www.marineengine.com/discus/icons/mime_pdf.gif""" align=left alt=""application/pdf"">Tech Bulletin
[url=""][b]97_08.pdf[/b][/url] (50.4 k)</td></tr></table></center>"
 
A huge thank you Troy. Lots of

A huge thank you Troy. Lots of info there. It'll be a few weeks before i can work on the boat again.
 
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