any hope for more power in 305 ci?
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any hope for more power in 305 ci?

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    Senior Member badbug3's Avatar
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    Default any hope for more power in 305 ci?

    20 ft hurricane fun deck and it has the 5.0 305 chevy small block engine. It runs great, but not enough power and speed. Is there anything worth doing to it to gain some power and speed? It has the alpha one drive. It runs 50 mph like it is. Would thru hull exhaust and a cam change and or intake change do much for it ?

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    You could do a few things but would be better served building a stout 350 or 383 engine.

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    Senior Member Robert Jonsson's Avatar
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    agreed. sell your engine complete and pickup a new (or used) 350 or 383. something with a much better foundation. in the mean time, it wouldnt hurt to put a thru transom setup on it. that wouldnt be a waste since you can hook it up to the new motor. i dont know much about what an alpha can handle. but you need to look in to that too, to figure out how much it can take before needing an upgrade

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    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
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    Other than a blower to increase the torque, no, not much.

    As advised above, consider a bigger motor, and build it apropriately. You'll be much happier in the long run.
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    cfm
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    Badbug3 -
    Is it a Vortec ? If not, what year/style ?

    Either which way, a cam and intake upgrade will help a lot. If you keep it mild than expect about 30hp or so. Assuming you already have a 4bbl set-up.

    I wouldn't worry about the exhaust at this level.

    Yeh, a 350 is better than a 305, but a 305 will respond the same way a 350 does to normal improvements. Up to a point of course. LOL.

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    Senior Member badbug3's Avatar
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    engine is a 1990 mercruiser with a quadrajet carburetor. Has very little hours.
    What manifold and cam would you recommend for power increase and at what level would thru hull exhaust make a difference? thanks

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    Senior Member Robert Jonsson's Avatar
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    bottom line. youre gonna spend a couple grand on exhaust, cam, and intake. probably gonna want to change that carb while you're at it. your gain will be in the area of 30-50 h.p. (just a guess). a lot of money for very little improvement.

    ultimately your weak link is gonna be the cylinder heads and size of the motor. not to mention the drive. i am not trying to discourage you. i think making boats faster is awesome... but i suggested an engine swap, so you can go to something that already has a better set of heads, a stronger bottom end, and more cubic inches... sometimes it is cheaper to just sell what you have complete and upgrade to a better package. do the math... in the meantime if you think that sounds like too much then my suggestion is to do upgrades that could be used with an eventual engine swap (i.e. exhaust).

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    cfm
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    Intake:
    http://store.summitracing.com/partde...4&autoview=sku

    Edelbrock #2604 is for quadrajet and '87-'95 heads. Make sure you wire open choke door to your carb if not an electric choke.

    Cam = really depends on if you don't mind changing the springs and checking retainer to seal/guide clearances. I'd look at Comp's XM256H which has following specs:
    256°, 262° at .006
    212°, 218° at .050
    .447, .462 lift / 112LSA / I believe installed at 108 ICL


    If you are unwilling to change springs and such and if above cam won't let you do so, call Comp and Crane. I believe they both have cams for fuel injected OEM car engines that will fall into this category of 'no other work needed.' Remember, these won't give as much ooomph though.

    As far as 305's go: don't tell the 305 in the below vid that it's not worthy. LOL. We got a spec'd hydraulic cam for it and added RPM Air Gap and Holley 600. It's spends most of it's life north of 6k.

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