Help me pick a cam
#5
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The Manifolds are stock. As far as the cam goes, I looked through my Comp catalog and they make two different Xtreme marine cams that might work. The first is part # XM262H and the second is XM256H. Comp says that the 262 is the biggest cam that should be used for an inboard/outboard application. This seems a little small to me, alot of guys on this board seem to be talking about the 280H cams automotive cams which have a bunch more lift and duration. What do you think I should use? Also, will upgrading cams really sucks down a bunch more gas?
#6
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You cannot install any larger camshaft before you get aftermarket exhaust manifolds and jacketed risers that move the water mixing point down the exhaust path. In addition, I would not install just a cam, you should also upgrade the intake manifold and carburetor to realize the improved flow. It is very easy to overcam a marine engine, be conservative with your selection.
#8
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Upgrading the exhaust on a stock Mercuiser engine shows limited improvement. Upgrading the exhaust is the first step when considering performance modifications. It allows more duration in the camshaft without reversion issues and better flow. I personnaly prefer an air gap style of intake, single plane over dual plane because of fuel distribution issues, but that also depends on power output.