Rochester 2GC Main Jet Change for Ethanol Gas

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Dtruedog

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Jul 20, 2012
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I have a '89 Cobra 2.3l in a 20' cuddy cabin boat. I run a minimum 89 octane. Where I live the only fuel available has up to 10% ethanol content. I know the engine doesn't put out the rated Hp as it would with straight gasoline. I am seeking feedback on the merits/faults of replacing the main jet (Roch. 2GC) with one or two larger orifice to richen the mix a bit in an effort to develop greater Hp. Any ideas or experiences in doing this?
 
Howard Sterndrive

Howard Sterndrive

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Re: Rochester 2GC Main Jet Change for Ethanol Gas

10% ethanol won't make any noticeable difference in power or performance and certainly doesn't require re-jetting.
However, "104+ Octane Boost" (if they sell it down there), will help reduce knock and ping enough that you won't have to retard the timing to get rid of it.
 
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Dtruedog

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Re: Rochester 2GC Main Jet Change for Ethanol Gas

thanks for the reply.

The engine is timed at 8 BTDC whereas the OMC manual calls for 10. In particular, the manual cites the 2.3l should not be detuned to accommodate lower octane fuels. Any idea why this engine would be singled out?
 
D

Dtruedog

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Jul 20, 2012
Messages
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Re: Rochester 2GC Main Jet Change for Ethanol Gas

Come on y'all! Surely someone has a learned explanation for the timing question. It's in the OMC Cobra shop manual. It's a basic Ford 2.3 (L4)???
 
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