Being a 7.4 instead of 454, your WOT rpm is 4200 to 4600 and 310 HP
Don't know which plug that is but its the wrong one (extended), should be MR43T, RV12YC4, BPR6EFS

plug is ac Delco r42LTS. I’ll get the right ones and swap it thx. Will do compression test when I’m pulling them

I believe the L29 7.4’s take the LTS Delco’s, so, MR43LTS if the late Model L29. Also, NGK BPR6EFS that merc specifically lists.

Thanks for the info I’ll get the correct plugs

Parts lookip, mercruiserparts.com .
Enter your motor vin . Go to Distributor/ignition parts. :)

A 25 Outlaw with a 415hp 502mpi should run about 62-63 mph with a 23 Mirage Plus prop.
With the 7.4, you should still be running a 23 Mirage Plus but at around 4600rpm for prob 55-56 mph.
Are you possibly in a higher altitude area???

Would be good to know what the serial number is

'96 7.4 LX MPI's here and engine label says 4600-4800 rpm.

Guess the manuals need updates, neither 16 or 23 list that for MCM or MIE

I'm in dallas texas, so basically sea level. I found a couple bag plug wires and swapped them and was able to get her up to 49mph with 6 people in the boat this weekend. Im about to change the cap, rotor, wires and already have new plugs in it. Also going to service the fuel injectors. Think I'm pretty close to having her run right. Just those two wires and plugs made a huge difference! Before it felt very restricted, probably because 2 of the cylinders weren't getting proper spark. Now it feels smoother and planes much faster and less effort