Re: More HP Top end for 96 5.7 mercruiser
Moore's book, while outdated a bit is dead on for relatively simple things like this...
you can go nuts on cam options, but remember that most people tend to overcam and unless you hwant to take forever to get on plane, you need the torque down low.
first and foremost, you need decent exhaust if you're going to look for power - and I'm talking about the manifolds, a spendy proposition. The only way to go cheap is to pick up longer stainless risers for the merc manifolds. They still have the wet joint leak possibility but will help a lot with reversion (much larger cam then stock and you run a real risk of sucking water back up from the exhaust into the cylinders, water doesn't compress like gasses do, you get the picture). cheaper, can weld extensions onto the riser to let the water mix further down the tube - no gaurantees on this one.
Revolution and kodiac are supposed to be a decent product, and on the order of a grand for new manifolds and risers,
next is imco thumperpower aluminum, good for some weight loss and ,maybe a little more expensive, plus imco makes great products overall,
then come emi's set up, stainless marine, imco powerflows, and dayna in the 1500 - 2500+ range, tubular headers more like 3000-6000. if you think it through and take time, you can get lucky on this though - I scored polished imco powerflows off a guy in nevada (never been mounted) and the matching risers off ebay, combined under a thousand. just be careful, a mistake here can turn your engine into an anchor in no time.
Some possible options (backyard hack who did a lot of research before building current engine).
mkos set up with the stock vortec heads and crane cam, edelbrock performer intake and 600 cfm carb of your choice would net a nice power increase for modest money. In my hands the edelbrock marine carb (1409) is relatively cheap (ca. 300) and a snap to tune - it should also be jetted real close to right straight out of the box for your engine. quadrajets do great when set up and holleys, others, too. (this wold also be great with the comp cam mtnrt recommended)
Next step up might be worked vortec heads or world products or dart heads with wedge combustion chambers and in the same chamber volume as your stock heads. You're talking about a thousand for new heads already assembled. 180 or 190 cc intake runners, aluminum at a little higher if you boat in freshwater only. same cam and intake or airgap rpm might make some difference, with the modified vortecs you can run a little more lift / duration where the valve lift counts by adding 1.6:roller rockers. You could also think about goign with a comp xm270hr
next step would be a set of good aluminum heads like afr 180's a little more cam, something like the next step up in lift and duration in the same or similar crane series, comp cams extreme marine xm276hr, edelbrock airgap performer rpm, etc...
Just some thoughts, bottom line is that if you don't have experience in fitting everything or a lot of patience and willingness to dig and learn, it would probably be money well spent to engage a machine shop that builds amrine engine sif you want to do much at all....
if you really want to hit the 70 mark, plan on 5k + with a good engine builder that's built marine engines and a 383 stroker engine.
and yes, cast components will work if you aren't running hard and fast all the time. I have this little problem.. I can't seem to run anything below half throttle for very long...
Moore's book, while outdated a bit is dead on for relatively simple things like this...
you can go nuts on cam options, but remember that most people tend to overcam and unless you hwant to take forever to get on plane, you need the torque down low.
first and foremost, you need decent exhaust if you're going to look for power - and I'm talking about the manifolds, a spendy proposition. The only way to go cheap is to pick up longer stainless risers for the merc manifolds. They still have the wet joint leak possibility but will help a lot with reversion (much larger cam then stock and you run a real risk of sucking water back up from the exhaust into the cylinders, water doesn't compress like gasses do, you get the picture). cheaper, can weld extensions onto the riser to let the water mix further down the tube - no gaurantees on this one.
Revolution and kodiac are supposed to be a decent product, and on the order of a grand for new manifolds and risers,
next is imco thumperpower aluminum, good for some weight loss and ,maybe a little more expensive, plus imco makes great products overall,
then come emi's set up, stainless marine, imco powerflows, and dayna in the 1500 - 2500+ range, tubular headers more like 3000-6000. if you think it through and take time, you can get lucky on this though - I scored polished imco powerflows off a guy in nevada (never been mounted) and the matching risers off ebay, combined under a thousand. just be careful, a mistake here can turn your engine into an anchor in no time.
Some possible options (backyard hack who did a lot of research before building current engine).
mkos set up with the stock vortec heads and crane cam, edelbrock performer intake and 600 cfm carb of your choice would net a nice power increase for modest money. In my hands the edelbrock marine carb (1409) is relatively cheap (ca. 300) and a snap to tune - it should also be jetted real close to right straight out of the box for your engine. quadrajets do great when set up and holleys, others, too. (this wold also be great with the comp cam mtnrt recommended)
Next step up might be worked vortec heads or world products or dart heads with wedge combustion chambers and in the same chamber volume as your stock heads. You're talking about a thousand for new heads already assembled. 180 or 190 cc intake runners, aluminum at a little higher if you boat in freshwater only. same cam and intake or airgap rpm might make some difference, with the modified vortecs you can run a little more lift / duration where the valve lift counts by adding 1.6:roller rockers. You could also think about goign with a comp xm270hr
next step would be a set of good aluminum heads like afr 180's a little more cam, something like the next step up in lift and duration in the same or similar crane series, comp cams extreme marine xm276hr, edelbrock airgap performer rpm, etc...
Just some thoughts, bottom line is that if you don't have experience in fitting everything or a lot of patience and willingness to dig and learn, it would probably be money well spent to engage a machine shop that builds amrine engine sif you want to do much at all....
if you really want to hit the 70 mark, plan on 5k + with a good engine builder that's built marine engines and a 383 stroker engine.
and yes, cast components will work if you aren't running hard and fast all the time. I have this little problem.. I can't seem to run anything below half throttle for very long...