Originally Posted by Drew555

[IMG][/IMG] this is the same set up. 383 alpha drive 425 hp turns 6000rpms chiped for 6500

Originally Posted by 94sylvan

I have a 94 sylvan 209 Barrritz with a 5.0LX merc i/o. I am planning to change engines this offseason. I have a new 383 that my father built and never used. It has 4 bolt mains and a SCAT comp cast crank. I am planning to use either Edelbrock aluminum ETEC 170 or cast iron vortec heads to get the compression ratio down to 9.3:1. Also using an Edelbrock performer dual plane intake with 600cfm Holley 4 bbl marine carb. Comp Cams Xtreme Marine flat tappet hydraulic cam with 1.5 roller rockers. I will have to modify the vortec heads, if used, for the increased lift. I plan to re-used the Thunderbolt IV ignition, and stock exhaust manifolds for now. Currently the exhaust is thru prop only, but as part of this swap I plan to remove the Y pipe completely and go dedicated thru hull. Future plans include CMI E-top small block headers and MSD ignition as budget allows. This combination should yield 335 hp / 390 ft.lb. torque through the stock exhaust.

Questions:

Is the 600 holley enough carb with marine exhaust? Or do I need to go with a 750? Or should I keep my quadrajet?
600 Holley at min, depending on head and cam choice.

Is it worth spending the extra $700 on the aluminum ETEC heads to cut 35 lbs of stern weight?

Ist it worth the $700 upgrade to go hydraulic roller cam and lifters? The roller cam has faster ramps which increase flow without making reversion an issue. Worth every penny, assuming you are running a good flowing head that will benefit from the cam.

Has anyone ever installed thru hull exhaust on a boat like this one? The swim platform forces the outlets very low (at water level when stationary). Side exit isn't possible either due to hull shape and contours. I can get it done with 3" manifold riser spacers then (2) angled elbows per side to spread the outlets and match the transom angle for exiting. I'm doing this mostly to get the heat out of the outdrive.

I would like to put the gen 1 alpha 1.32 upper gears in if they fit???? to help reduce torque multiplication and drive stress from the increased engine torque. What else should be done to the outdrive to help it survive? The drive is original and I do plan to blueprint it this winter to replace any suspect gears / bearings. Keep the 1.50. Drive shower, remote resevoir change oil every 25 hrs, no hard hole shots.

Can the alpha water pump keep this engine cool? Can I ditch the circulating pump and install a crossover cooling system with thermostat to eliminate another 20 lbs from the back of the boat? Or are these more of a racing setup only?
When I ran SBC, I never ran the Merc circ pump. Always relied on the Alpha pump with never a problem. Just replace the impeller every other year at minimum. I put a new one in every year to be safe.

Is the Thunderbolt IV ignition good enough for this combination or will I have problems?
Should be fine.

Will the stock mechanical fuel pump be adequate?

Thank you in advance for any helpful advice that you can send my way.

Originally Posted by Drew555

[IMG][/IMG] this is the same set up. 383 alpha drive 425 hp turns 6000rpms chiped for 6500