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Topic: MERC 5.7 EFI conversion to MPI

Author Message Prev Topic | Next Topic  bannister "Seaman Recruit" Joined: December 05 2009 Posts: 24 Posted: September 12 2010 at 12:49 | IP Logged Here is a question for a MERCRUISER guru. I have a 2000 5.7 EFI 260hp Mercruiser in my Doral 250SE. I also have a complete injection system (intake, injectors, distributor, wiring, ECU, fuses etc) from a 5.7 MPI 300hp. The question is if I change all that on my engine, 1. will it work? 2. will that make my engine 300hp too? As far as I know and from info around the internet, everything else between those two engines is excactly the same (comp. ratio, engine block, internals, cam etc.) Any ideas? Back to Top    bannister "Seaman Recruit" Joined: December 05 2009 Posts: 24 Posted: September 14 2010 at 13:52 | IP Logged ok, here is the project one more time. Engine is a 2000 5.7 EFI. Remove ECM, wiring, throttle body, intake manifold and fuses. New parts out of a 350 MAG MPI. Install new ECM, wiring, intake manifold, injectors, throttle body and fuses. No need for matching ECM's or reflushing, rewiring or cam change. Everything OEM. Exhaust and all other parts of the engine are the same between those two. We are not talking for a car engine with headers and muflers restricting the flow. The diameter of that exhaust can support twice that horse power. The goal is not the extra 400rpm (and more consuption) BUT MORE TORQUE at the SAME RPM resulting to more BHP. (due to better volumetric efficiency from the intake manifold and multi point injection.) Back to Top    bannister "Seaman Recruit" Joined: December 05 2009 Posts: 24 Posted: September 14 2010 at 13:52 | IP Logged Today confirmed my theory with a Mercruiser certified mechanic. The conversion is possible with no problems. It will make my engine a 300bhp. And yes, the 40bhp difference is coming from more torque produced at the same rpm due to the manifold, throttle body and more precise injection. So, if you have a 1996 and up mercruiser block with Vortec heads, go to a yard and look for 350 MAG MPI leftover parts...... Back to Top

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