MPI w/ a procharger
 

My buddy is interested in a newer boat that has a procharger on the 7.4 MPI. His concern is the cast short block. The boost is 4-5 PSI. Seems to be a tried & trued setup, does he have anything to worry about w/ this setup?

I know of 3 cast 7.4s in this area running boost, and 2 cast 496's running boost as well. They are all running with no issues, infact one is a 1995 with 600hrs on a 177 blower for 4 years.

Here is the deal, with added boost you run a higher risk of detonation, and detonation with cast pistons does not give you much time to react, a ping is the last thing you might hear before a rod makes an apperance in your bilge....unless you follow the rules!

Running boost on those engines require some simple rules-

Run conservative timing
Never run questionable fuel, never!
Always start the season with fresh fuel and fresh fuel system maint
Ignition must be maintained to the highest standards


Make sure the ECU is flashed for boost, and if you can find a reflash for ethanol use I would get that done as well.

All of the items listed are normal for a high performance boat, but with a stock 330 you would only need gas and oil :)

The good news is a 24-26ft boat gains 7-10 mph with 4-5 of boost.

IMO go for it

I would pass on any used boat with a Procharged 7.4MPI.

Depends on if it is a good deal. If it pops and he wants to go back to stock that used procharger will just about pay for a 330 long block :)

I know its not ideal but as 4bus points out it does seem somewhat common w/ out issues. I've always heard 500-550hp horse is fine w/ a cast short block. I doubt 4-5psi on the mpi would be anywhere close to that?

What makes you think twice about it?

Cause its "Knot for him" :D