400 sbc upgrade. Efi options.
 

Hey everyone I'm currently building a new engine for my 1986 Chaparral Villain III. It currently has a carbed 305 in front of a cobra 1 outdrive but all that is going away. I'm building a 406 sbc, 64 cc vortec heads, flat top pistons, steel crank, 3.75 stroke. Hydraulic roller Cam, lifters and rockers. 249-SK12-418-8 is the Cam. Fresh water cooled. Bravo 3, 2.0 ratio currently. But I also have a 1.5 and 1.8 bravo 1 lower I may use. 26p prop. My problem is fueling. I have a stock Mercury marine mpi system off of a 350ci and would like to use it but I'm not finding many tuning options for it. I don't have want to use a carb as the engine will be on and off a ton for towing. Does anyone have any experience with tuning mpi or is there another aftermarket efi system? Thanks.

Ditch the Bravo 3. Use a 1.5 Bravo 1. You will need a new prop, likely a 4 blade Bravo 1 in 22" pitch or Rev 4 in 19" pitch for starters. I'd need to see exactly with 350 MPI system you are referring to to make any other suggestions and also which MEFI controller you have. MEFI 1, 2 3, or 4 would work and could be tuned via yourself with software. Other option is the Holley Marine stuff. Have yet to hear any real negatives other than initial cost. Go with 4" thru hull exhaust and make sure you can spin it to 5500-5800 rpm as that will likely be peak HP. Prop accordingly.

Tuning software is dependent on the system you are using. If using a MEFI 1, 2, 3 or 4 you could use MEFI Burn. The Holley Systems come with their own software. You would also need to verify what flow rate injectors you currently have and have them cleaned and flow tested. If they are insufficiently sized for the HP you intend to make you would need higher flowing injectors.