2.5L 120hp Carb Issues

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beechhouse

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Mar 19, 2011
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I have a 1988 SeaRay Seville with a 120 hp 2.5L. At some point in time someone took the original carb off and put the carb off of a 3.0L on it. I rebuilt the carb this last winter and the engine starts and idles but at speeds less than 2000 it runs rough. On plane it runs like a champ! Since it does not backfire it has plenty of fuel, too much I think. Does anyone know if the jetting is the same on the 2.5L vs. 3.0L. I checked all the standard items, timing is good, new points and condenser, plugs, wires, and it has great compression.

Any carb thoughts? I think the original was a Rochester and now has a mercarb.

Any inputs are welcome
 
CobiaXL

CobiaXL

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Mar 8, 2010
Messages
353
Re: 2.5L 120hp Carb Issues

Check for vacuum leaks around intake and carb base gasket,Sometimes the linkage bushings in baseplate of carb can leak air as well.Spray some flammable carb cleaner while running engine around the known areas to see if idle picks up.....Make sure you have no raw fuel dumping in carb at idle..Carb should look dry when at idle.Sounds like a high float to me.I don't see any difference in jet
 
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beechhouse

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Mar 19, 2011
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14
Re: 2.5L 120hp Carb Issues

Good ideas, I will check the float level and the throttle shaft.
 
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beechhouse

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Mar 19, 2011
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Re: 2.5L 120hp Carb Issues

Well I adjusted the float a little higher than what it was and leaned out the idle adjusting screw, it runs a little smother but still not like a fine tuned V8! i guess it is a iron duke (puke) after all.
 
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Fordiesel69

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Sep 18, 2009
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1,146
Re: 2.5L 120hp Carb Issues

Nope, not an iron duke. If anything, LOWER the float level slightly.

May have luck finding a rochester on ebay or local CL.
 
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beechhouse

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Mar 19, 2011
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Re: 2.5L 120hp Carb Issues

You are correct, I bent the float down, which lowers the fuel level. I was working with the lid upside down so making it higher actually lowered the fuel level. Confused yet? Any other tips to makew the old iron duke run smoother?
 
kilowatts

kilowatts

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Apr 3, 2009
Messages
299
Re: 2.5L 120hp Carb Issues

Hi Guys:

The only advice I have is that if you know the carburetor is a non matching replacement and it runs rough, then I would get the right one and install it.

kilowatts
 
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