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crmax
10-06-2001, 11:35 AM
which is the better motor in a 20' boat the 5.7 mag or 7.4mpi?

SUPERCREWJOHN
10-06-2001, 12:02 PM
Originally posted by crmax:
which is the better motor in a 20' boat the 5.7 mag or 7.4mpi?
We need a few more details? What type of boat? What power option( Jet,Outdrive, V-Drive) Also, The 7.4 MPI has been discontinued by Merc, and has been replaced by a 6.2 320HP or the MERC 496 MAG ( 375HP)
Depending on power option the 350 Mag or 6.2 will probably be fine if it is an I/O. If it is a Jet, there really is not a substitute for cubic inches due to the fact that Jet Boats( the Pump actually) need more torque to push the water http://free.***boat.net/ubb/biggrin.gif
Hope this helps, but please provide more detail because their are some expects on this boat who can direct you based on the specifics of the applications and hull type/brand.. http://free.***boat.net/ubb/eek.gif

racingrascal
10-07-2001, 09:06 AM
I think bigger is better, but John is right. What is the drive unit? Jet or I/O? If jet then big block if IO then the small block will be just as fast as a big block jet. What kind of speed you want and gas mileage.
Andy

crmax
10-07-2001, 06:41 PM
the drive is i/o, just curious on the pros and cons. I have the 7.4 and had a debate over the two. I said that the 7.4 wins because you dont have to get the high rpms

boatnam2
10-07-2001, 07:08 PM
hey crmax,a few years ago me and my buddie bought identical boats 21ft ultra's except mine had a 350 mag alpha and he had the 7.4 non magnum.at the time i think they were 260 and 310 hp respectively.i got the magnum cause of the hype, i thought is was stronger and better but in reality at 300 hp you dont need a steel crank.he got the big block because of more power at the time they where the same price.if i did it all over again i would of got the big block no questions asked.it just has a lot more umph.both boats are still running with the original motors 9 years later.he still has his and i see my old one all the time at the river and the guy says it run's great.