Octane of fuel recommended for 330HP 454...
 

What octane fuel are you guys running in stock 330hp 454s.

Thanks.

89 should be OK

87 should be just fine also. My 496ho's only require 87.

87 is the minimum but 89 should give you slightly better performance and is better for the motor all together.

87 octane is minimum and running any higher octane is waste of money and will possibly hurt performance and for sure will not help performance.

Agree

Will 93 octane hurt a 454 Mag EFI, Griff?

No,,but not needet !!! 87 is just fine !!

87.

It won't actually hurt it, but it will make your transom more black. The higher octanes won't burn as completely on an engine designed to run 87. 87 will burn the most completely and make the most power.

This is true. I have seen a 525 boat that used 93 octane and that transom was covered in soot!

If you always run premium fuel you can bump the timing a bit for some added power. The down side would be if you do that you must run premium fuel or risk detonation. If you dont know what your doing dont do it and run 87-89 octane with stock timing.

I assume you have 7.4 MPI's. I run 87 and every third tank gets fuel injection cleaner. In the past I had run 93 every third tank to clean the system but it surely didn't make cleaning the transom worth it.

I'm not sure what years this applies to, but at one point in time, the merc engine management sytems would advance timing until the knock sensor detected ping, and then back the timing off a certain amount. Running 93 octane would actually keep the knock sensor from going off, and thus the box would think something is wrong, and dial timing back all the way - so you would actually loose performance by running higher than the prescribed octane. And, I think you'll also find that the idea of 93 octane "cleaning" things out is nothing but good marketing......people do it in their cars thinking they are treating it to something special.....total waste of money if the cars system is not set up for the higher octane....

I've seen 502 Magnum EFI dyno sheets. Lost 2 hp using 93 instead of 87. If you don't have the compression or timing to take advantage of the higher octane, you are losing power. Higher octane is harder to ignite, therefore more detonation resistant.