Hi everyone, I am wondering if I should keep the same manifold or upgrade. My intakes now are the Edelbrock Air Gap dual plane style. They have been on the engines since 2010 and I am concerned about the water passage where the head meets the intake possibly rotting and leaking water into the engine.I like to catch problems before they start. I boat in bracish and salty waters. I do wash the engines after each use though on a garden hose. My question is, Should I upgrade to a single plane intake? My friends boats all have single plane intakes. Some are running HP 500's some larger. Will I gain anything from a single plane?
My 509's were dyno'd @ 490 HP @ 5200 rpm with the dual plane intake's.

Thanks ahead for your input

where you are if I were having to change I would go to the Dart like the 500hp...

I actually have a single on one of my engines and a dual on the other. (I'm just lazy) I've said for a while that I can't tell the difference same RPM's. But at the end last season I realized I had a bad coil wire on the single plane engine. After cutting it back and crimping it together again the single engine now pulls about 100 more RPM's. Take it for what its worth.
BTW Dart style

I had an extensive thread up on here a couple years ago with a lot of good feedback. If you do a quick search, you will find it. Unless you really have a large heavy boat, the low end torque that the AG develops is not needed. A lot depends on the displacement, heads, cam, and intended RPM range.