I have an 87 Four Winns with a cracked block but has a new mercruiser outdrive. It had a mercruiser v-6 and have been offered a cobra v-6 replacment.Will it switch out,and will it match up to the mercuiser outdrive? I also have the only automotive motor(so I was told) that I can replace the 87 Mercuiser motor with that came out of what they said was an 85 Chevy Astro van,although the #s on the motor say it's an 86,that came with a 4" highrise intake,4 barrel Quad carb,and factory headers. I was told that if I switch to marine gaskets,change the cam over along with all of the marine components(including the external fuel pump), it should work. Now I plan to use the intake and carb off the original motor,but i'm getting two different stories.One from the marine group,and one from the standard(but intelligent) mechanics.The marine group say's if I don't use the cam from the mercruiser,the automotive cam won't handle the higher r.p.m.'s. Can anyone ease my ongoing confusion as to what to believe here? P.s. I've also had the flywheel professionally balanced to eliminate the vibration possibilities!! Help please?? Thank you!