Ken N

Does anyone know what a good cam upgrade, for a 1999-502 MPI 415 HP .

Griff

didn't you like the last answer????????

http://www.offshoreonly.com/forums/s...d.php?t=159162

My suggestion would be to get a complete package from a reputable builder instead of trying to piece together your own setup. The package will be proven with dyno numbers and an an ecm recalibration will have already been done.

Ken N

I have a silent choice style exhaust system. I need a cam that is compatible with it.

tblrklakemo

Shouldnt make any differance.....the diverters that is. Manifolds and risers are a different story.

Griff

You are not going to be able to run any upgraded cam with the stock cast risers. It dumps too close to the exhaust manifold.
The 500efi and 525 cam are both capable of being run with silent choice diverters, just not the factory 502mpi manifold/risers. Also, without some good exhaust, you are not going to see the real gains of any upgrades.

KAAMA

He said it right. One of the most important mods when upgrading for more power is swaping out the stock Merc cast iron exhaust and risers with all it's choked down, crude 90* elbows and replacing it with a better breathing manifold and smoother transitioning tailpipe style riser. For the most part, a better breathing exhaust system must be first on the mods list when looking for more power, otherwise you're just going to be chasing your own tail in circles.

Croozin2

Kaama nailed it. You can try to shove as much air into the engine as you want but if you can't get it out...

Remember, an engine is nothing but an air pump. Start with a good exhaust system. You'll be glad you did.

Ken N

I did not expect such a response. I left a lot out. I have already installed a set of cyclone S.S. Headers, MSD-6M control box distributor and coil, K&N large size flame arrestor. What I have on hand is a set of 308 Dart Iron Eagle heads (2.250 intake, 1.88 exhaust and 119cc combustion chamber) and a set of Comp Cam roller rocker arms, Cloyes timing chain. I plan on swapping out all the parts at one time. The only thing I need is a cam. I am concerned with water inversion.
Any help on choosing a cam would be appreciated.

Griff

Get some flow numbers on the heads and PM "rmbuilder"

You should not have a reversion problem with either the 500efi of 525efi cam, but I think you should get a custom grind to fit your head flow numbers.

The ECM tune will be tough part without the engine on a dyno.

KAAMA

RMBuilder/Bob Madara of Marine Kinetics in New York. (585)654-8583. Bob is high on the list of referals and has helped many here when it comes to marine cam applications.