Donziweasel

Time to upgrade power in my Donzi 18 classic. Stock 350 mag mpi. Thinking of building a 383 stroker out of it. Will the stock Merc MEFI 4 fuel injection work on a 383? Thanks!

GPM

Depending on HP increase you may need injectors and re-tune.

Trash

Yes, it will. Easily. As GPM mentioned verify your injector size. Pull them, clean and flow test them. Target your HP level and then select your injector size. The year and serial number of your engine will help get baseline information. You likely have a 36 lb/hr injector, but verify this. A 36 lb injector will carry you through about 450 hp at 80% duty cycle.

You will need to modify your bin file in the MEFI 4. There are those out there and on this forum who can do it for you. Or, you can do it yourself with the appropriate knowledge and software. Keep it simple. Logically modify your motor paying attention to the peculiar limitations for marine applications. I could go on but will let other chime in.

Donziweasel

Thanks. I thought Merc used the same injectors on the 350 to the 502, but I could be wrong. I will check. I heard Mark Boos can tune an ECU for a stroker.

Donziweasel

Actually, they are 24lb. Need to upsize?

Unlimited jd

iTrader: (5)

What about buying a merc 383 mag mpi? Turn key complete with a warranty

Trash

Yes you would. I run 42 lb injectors in a 377 stroker. I've done what you want to do except I had a 95 pre vortec Mag EFI/MP motor with the tunnel ram Scorpion style intake.

I've spoken with Marc Boos. He doesn't do much small block stuff. Those are his words, not mine. I'm sure he's capable, but he's not the only source.

Regarding purchasing a 383 Mag MPI, you can build an equivalent or better motor with better parts for the same price or cheaper. A turn key Merc crate motor will definitely give you quicker turn around time though.

Best of luck.