454 Mag or 7.4L??
 

Hello,

I am trying to identify which motor is in my 97 Shabah SS, the 454 Magnum or just a regular 7.4L

I know I could get a serial number off the heads under the valve cover but I would like to do it without cracking the motor open for now if possible.

The engine serial number is OKO38027. If I look this up on the Mercruiser site it lists both the Magnum and the 7.4L

Any ideas? Thanks!

Re: 454 Mag or 7.4L??
 

I know this was already addressed in the other thread but they are one in the same, and a beast of a powerplant! Enjoy your Mariah :wink_thumbup:

Re: 454 Mag or 7.4L??
 

You have a photo?

While 7.4 and 454 are similar displacement they can be very different motors. 7.4 usually refers to the 310 MPI motor while 454 tends to refer to the 330hp 454 MPI or 385hp 454 MAG MPI motor. You will find the 7.4 is said to have the peanut port heads while the 454 has the big rectangular ports.
7.4 vs 454

Re: 454 Mag or 7.4L??
 

I can get a photo tomorrow. Mine is carbureted. I know there are a ton of internal differences, I am just trying to figure out which one I have with out breaking it apart. My last idea was to pull a valve cover and see what the head casting numbers were, but after I tried I realized I would have to pull an exhaust off to get to a couple of the VC bolts. Boat is winterized and its full so I am not doing that yet.