New poject is to build conservative 550-600 HP 540 storker engines out of my stock merc 502s. Boat is a very heavy express cruiser with arneson drives and will be used at 40mph fuel efficient (relatively speaking) cruise 90% of the time.

Build not finalized but assume:
Scat 540 assembly
Holley 850s
Stock Merc iron heads with fresh valves/iconel/2.25/1.88
Crane 741-type CAM
Gill SS wet exaust
Intake?????

Not too concerned about WOT or high rpm running and am a bit confused about single versus dual plane intakes on a 540:

Which one to use and why?
Does the dual enhance torque but kill top end?
When does single plane kick in - at what rpms?

As always - thanks experts!

it sounds to me like you want a dual plane but for that sort of usage, a good clean either factory or aftermarket mpi injection would be perfect. it would give you the best torque at the precise rpm you want with the very best fuel economy you could get. money very well spent in my opinion.

For as heavy as your boat is, I would think a dual plane would work better for low and midrange torque.

Dual plane like an Edelbrock Performer. I would use a slightly smaller cam to get a power peak in the low 5000 area. Let torque move the boat. That way the motor will be happy cruising at 3500 rpm. Get better fuel milage also.

Dual plane performer and drop down to a 750 carb...will be fine and pick up MPG..Rob

I just put on a merlin dual plane intake with 850 wholley on my new 415hp 502 replacement long block. I just dyno'd them if you want the sheets.

Edelbrock Performer RPM Air-Gap (dual plane)

Yes I'd like to see them if available - pm them if you dont want to broadcast ;-)

Thanks