valves

[over board]

I own a 1996 253 convincer with a 454 mag efi mp with a pro-charger m-1sc running 5 lbs. of boost. I wanted to know if I should change the head gaskets and the exhaust valves? Some people tell me I already have iconnel exhuast valves others say I don't. I had the computer reprogramed, the boat runs great, I just want it to last. I have done 82mph on gps at 5300 rpms running a 27 pitch quad 4 prop.

[over board]

I own a 1996 253 convincer with a 454 mag efi mp with a pro-charger m-1sc running 5 lbs. of boost. I wanted to know if I should change the head gaskets and the exhaust valves? Some people tell me I already have iconnel exhuast valves others say I don't. I had the computer reprogramed, the boat runs great, I just want it to last. I have done 82mph on gps at 5300 rpms running a 27 pitch quad 4 prop.

[MikeW]

With 5 psi I think your fine. If you want to turn the boost up then, yes my need to look into what is in your motor. My Blown 509 I ran Cometic (sp?) head gaskets And I had a Dart block with dart heads. THe block had a little 4 tang on the block (two for each head) in the lifter valley and the heads where tapped to put a bolts where there was no head bolts on top over the cyl. this took care of any chance of blowing a head gasket. I ran 9 psi with a static CR of 8.0:1 all on pump gas. For Valves, I ran Manley Pro flows.

[Dave T]

Overboard,
The stock 454 mpi did not come with Inconel exhaust valves.

[vinny p.]

I agree with the above.. Your motor did not come stock with Inconel valves. I am a firm believer in using Inconel valves for marine applications. They should be stock in any peformance motor. But, as we know, Mercruiser cuts corners to maximize profits for themselves. So, in my opinion, any supercharged motor should be running Inconels and good head gaskets. The factor that would determine whether you absolutly need the improvements is how you run the boat. If you run it wide open for a long stretch, you NEED good valves and gaskets. If you only open it up occasionally, maybe you can get away from it for a while. While a supercharged motor is at W.O.T., the combustion chamber produces alot more heat than does a naturally aspirated motor. Thereby the need for Inconel valves and gaskets.