RHS claims my heads are finally shipping out this week. So it is almost time to start putting things back together, but I am in a toss up on carb CFM. All the online calculators say 600cfm is sufficent. But I am hesitant as boat motors are constantly under loads that auto's ever see. I am between a edelbrock 1409(600cfm) and the 1410(750cfm). With the build I am shooting for WOT right around 5400rmps. Lastly should I stick with the 8degree BTDC timing or is there a better starting point. The heads are the non-vortec style, I decided to go with the high performance aluminum heads instead. Here is the build sheet for the motors, stock bottom end merc 350's, with TB-IV ignition. I plan on running either rev 4's or mirage plus props, pitch to be determined later!

-RHS proaction aluminum heads 180cc runners, 64cc heart combustion chamber.

-Crane cams with advertised 224/224@050, 282/282duration and .465/.465 lift and 112LSA

-Crane 1.5 full roller rockers

-Edelbrock AirGap RPM intake manifolds

-New Crane coils, plugs and wires

I pray that this has been worth it, my wife is ready to shoot me! I went with a build sheet close to some I have seen in magazines and numbers should be right around 390hp/410lbft
I am hoping it will get the old classic tub up and moving!

Thanks guys for the advice. Hopefully I will see you Havasu boaters on the water soon!

700-750 cfm, stock 350 mercs use 750 webers(edelbrocks) I would want to be about 28-30 deg total timing, need set it up that way...that set up going to want to 5600-5800 RPM as well...

I had a similar motor built last year with the exception it was a standard bore stroker (377), Dart non-vortec heads, and a Crower hyd roller (221/230 @ .050 and .525"/.545" 114 LSA)using a tuned Merc EFI/MP system. Unfortunately I can't say for sure what the EFI throttle body flows. It has carried the motor through 5500 rpm though.

I'm also using the Merc EST ignition and have the base timing set to 8 deg. I'd have to get into the MAP/Spark Advance table to see the max timing I have in it right now. It's not that far off from the stock program however.

The Rev 4 or Mirage + may work depending on how heavy or light your boat is. I've had better results with the Laser and Mach Sterndriver. I'd like to try a Rev 4 for kicks.

750 carb,forget about base timing,set total at 34,30 makes the egt,s way to hot,and kills the exhaust valves,IT WILL NOT DETONATE AT 34 TOTAL.if you use 87 or 89 octane,back timing to 32 or 33.