Hello all......have a couple questions, 1- I have a '97 Mariah 252z shabah 7.4 /b3. My flame/carb cover is black with red lettering. I have seen some same year/engine covers that are black with light blue lettering?? Is there a difference between the two engines even though they are the same size and year? ........next question, my pitch on my props are 28's??? How or where can I tell what factory is suppose to be? This seems kinda high to me. Boat hits 2/300rpms shy of bottom end of rpm range.
Howdy,
I have a 1997 7.4L + Bravo III in my 87 Fourwinns 211 Liberator. (It was removed from a 98 24ft Bayliner) It's also a 1.81:1 drive and I have 24 and 26p props for it
I get about 4400 RPM with the 26's and a little over 4600 with the 24p props. I also have a 3x4 24p propset but I am not impressed.
97 7.4L engines include several models. ( reg 7.4 [carb], 7.4LX EFI , 7.4LX MPI (all rated 4200-4600 RPM)
There was also a 454 Mag MPI (4600-5000 RPM)
Your serial number will reveal exactly what you have.........
What is your drive ratio, speed (GPS) and RPM at WOT ? (for your size boat, I'll guess 1.81:1 ratio?)
If your WOT RPM is 200-300 RPM below 4200, (turning 3900-4000 RPM) You are over propped. You need to switch to 26p or 24p propsets.
Select prop pitch to obtain 4600 (if that's your max) at WOT when loaded at the weight (people, gear fuel) you will operate.
Running over propped will slow your holeshot, top speed performance and can possibly damage the engine due to lugging (from possible detonation)
Regards,
Rick