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Replacing engine, do i have to change the setup on the carburator?

G

Garpen61

New member
My old engine is finnished, mercruiser 4,3LX from 1991. All is original, 2-port merccarb 175 hp.


The new engine is totally new 4,3 with balance shaft and Vortec intake. They told me it should become 190 hp with the same carburator.


In my head it would be logical that you have to open up the gas-side in the carburator to achive a good and healthy mixture?


Has anyone done this operatin, and what did you change to get it right?

is there a standard set-up for this engine? Engine number 2270542A.
 
Not sure what you mean in some of your posting....do you mean two barrel carb? When you say "open up gas side", do you mean re-jet? You will need to go to the manual, determine what main jets and power valve is required for the new engine, then check your carb, see what is currently installed.
 
no need. Your old engine was probably just rated more conservatively and at a couple hundred rpm less (4600 max). The way a carb works, is the fuel is added proportional to the air. If you rev the new motor to 4800 where it's probably rated, it will draw more air, and therefore more fuel automatically.
But once broken in, you'll want to look at the spark plugs after a couple wot runs and check for signs of too lean a mix.
 
hystat said:
no need. Your old engine was probably just rated more conservatively and at a couple hundred rpm less (4600 max). The way a carb works, is the fuel is added proportional to the air. If you rev the new motor to 4800 where it's probably rated, it will draw more air, and therefore more fuel automatically.
But once broken in, you'll want to look at the spark plugs after a couple wot runs and check for signs of too lean a mix.
Click to expand...

Thank you!

Then ill keep it as it is and keep an eye at the sparkplugs!
 
Your new engine being a Vortec design, is more efficient then the old one. That's how it develops the extra power with the same equipment on it. You don't have to change any jets, but I would adjust the idle mixture screws. At idle when fully warmed up, I would turn them out 1/2 turn at a time till you reach the highest idle speed, richening them up some, then leave them there, this should be the best setting for your engine.
 
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