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Merc 74L MPI how to get to Magnum

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gsferry

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I have a Mercruiser 7.4L (

I have a Mercruiser 7.4L (454) at 310 hp. What would it take to convert it to a 385hp 7.4L 454 Magnum?
 
"Not sure. Definitely a hotte

"Not sure. Definitely a hotter cam, possibly higher compression (requiring premium fuel) and probably different heads (with bigger valves and ports).

Jeff"
 
If you are looking for more po

If you are looking for more power you do not have to make it a magnum. Depending on what yearor mainly what cylinder heads you have and exhaust is your bottle neck on making more power.
Why do you want to make a magnum?
 
"Mostly just looking for more

"Mostly just looking for more horsepower. The reason I chose the magnum is because that would be consistent with this boat model, and better for resale. I've got a Captains Call through hull exhaust kit from Corsa that I'm going to install, but that likely won't yield any more horsepower, just better sound (to some). To get from 310 to 385 hp is tough to do w/o some major modifications.

Mostly just looking for what other may have done to gain horsepower on the same engine (Merc GM 7.4L MPI).

Thx."
 
"Basically,.........
You Can

"Basically,.........
You Can't get to where you Want to Be,.. from where you're At........

The 7.4l MPI is a Standard Production motor......

The 7.4l Magnum is a HO motor with Stronger Internals.........

Once you get passed the Bare Block,.... These 2 motors have Very Little in Common........"
 
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