Hey,

I bought a defect Mercruiser 502 Magnum MPI Engine (MY 1996 - Gen V).
Due to a failing impeller the engine overheated and the hardened valve seats felt into two separate cylinders and damaged the pistons and the heads.
Because the crankshaft isn't in good shape either I'm thinking of boreing the block to 4.500" and buy a new and balanced stroker rotating assembly (540cui).
My goal is to achieve about 600hp.

Has anybody a good recipe to build a 540 MPI engine or can review my following part list?

Part list:
- AFR 325cc Rectangle Port Cylinder Heads, with Full CNC-Chamber (121cc), Inconel Exhaust Valves and Springs for HYDRAULIC ROLLER .725 LIFT/6500 RPM
- Balanced Scat Stroker-Kit with Mahle Flat-top-pistons (-3cc piston volume)
- Stock rectangle port Mercruiser Intake manifold
- Stock Keihin Injecors (42lbs should work up to 600hp @ 80% duty-cycle?!)
- Throttle-body bored from 60mm to 68mm
- CMI 454/502 E-Top headers
- MEFI 1 Controller (I'm, able to adapt the parameters and maps with MEFIburn)
- Comp Cams Xtreme Marine 525 EFI Camshaft with retrofit lifters


regards
Tobias

agree with jd.........mpi is old and restrictive, go with a Holley system if its in the budget

Which cam would you recommend?

I have a 540 EFI that I have done everything to the MPI manifold that can be done and I have the TPIS big throttle body on it. Runs great but still runs out of air at about 5200RPM. I would love someone to try or use the PRO FLO XT Edelbrock manifold. I run Mefi 4 and boat was live tuned by Eddie Young.

The MEFI 1 is fine for his situation. It has plenty of variables for his situation.

The MEFI 1 will work great. It is simple and robust. The aftermarket systems are great, but you have a system that will work and work well, so I'd save the money.

I would invest in bigger injectors. I'm using 42 lb on a stroker small block. It leaves me a lot of head room. You might want to bump up the injector size a little as well.
There are aftermarket Keihin style injectors available that offer a little more flow.

I've done what you intend to do with a similar vintage small block package. Same TB, controller etc. Just PM me.

Last piece of advice. DO NOT CHANGE YOUR STOCK TUNE just yet. Keep it as that will be your starting point. And yes the new motor will safely start and idle on the stock tune.