I currently have a 5.7L Mercruiser inboard in my Malibu ski boat. I bought
it used and it came with the two barrel "mercarb" carburetor. What I am
wondering is what is involved in switching this engine over to a Four barrel
carb ( Probably a Carter AFB or a Holley 4160) and what kind of performance
gains should I expect with the new carb? Do I need a new intake manifold and
if so what type is best?

Any information would be greatly appreciated !

Thanks in advance!


matt

Hi,
Most all of the Mercs come with spreadbore carbs "GM Quadrajects"
whatever you decide you'll need a "Marine carb" with the fuel pump
blowout line. also you have a 2 barrel camshaft which i'm pretty sure
has different lift and duration than a factory 4 barrel cam but i
can't say for certain without checking. you'll need a four barrel
intake too. for the amount of performance you'll gain from going
to a four barrel hardly justifies the 5 to 6 hundred dollars for a new
marine carb not to mention intakes price. for the new 4 barrel to
be of any benifit to you the camshaft has to be capable of meeting
the proper air and fuel demands or you may end up worse off.

your best bet is to dig around for a good used Mercruiser intake +
carb and rebuild the carb, quadrajets are fairly simple to rebuild.
you may be better off spending your money on a good valve job
or quality tune up and experimenting with prop size.you will probably
get more bang for your buck.
Brian





On Wed, 03 Sep 2003 03:22:41 GMT, "matthew siroky"
wrote:

I currently have a 5.7L Mercruiser inboard in my Malibu ski boat. I bought
it used and it came with the two barrel "mercarb" carburetor. What I am
wondering is what is involved in switching this engine over to a Four barrel
carb ( Probably a Carter AFB or a Holley 4160) and what kind of performance
gains should I expect with the new carb? Do I need a new intake manifold and
if so what type is best?

Any information would be greatly appreciated !

Thanks in advance!


matt




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"Lakenut Mechanic, Brian K" wrote ...
: Hi,
: Most all of the Mercs come with spreadbore carbs "GM Quadrajects"

snip

What's a quadraject? This isn't a flame or anything - I have just
not heard of the word before so am looking for a quick
education -
Is this a misspelling of quadrajet (a term I'm all too familiar with)
or a GM name for something cute like a throttle body injector animal
that bolts onto a carb manifold...

You get my drift? _Drift_, hah - nautical humor!

Dave