just hard to keep these things from doing that no matter what it seems...

These are photos of both sets of heads from both engines. They all seem to be pretty much the same

that is reversion,i am 100% sure.

How bad of reversion is this ? What can happen from this? I know the remedy (extend the pipes longer so the water comes out father away) but I like the silent choice. Its been this way since I got the boat back in 2008. The exhaust manifolds were pretty clean by the ports. Dark exhaust stains only except one port looked like # 7 cylinder had some white residue. If it was reversion wouldn't there be some kind of water stain inside the SS elbow and the aluminum manifold.
Any other solutions?

smaller cam.

The face or gasket surface looks pretty rusty on some of the ports .could have been a minor exhaust leak leading to this as you have been running the same setup for this long. Definitely test for any leaks and downstream flappers as well.

I don't think you will ever stop this, looked a many and all have it to some degree, when you shut engine down, water drips into exhaust, as pressure bleeds off sits there, the heat from the engine seems to draw that moisture back to it....seen stock low H/P cam motors show same signs to some degree...

Thats not ideal . And everyone ,myself included loves the sound of a lopey cam at 800 rpm idling through the no wake zone and idling up to the cove . A radiator pressure tester with cone adapter and a tub of water will get you a quick test of manifolds and risers and make sure you have a thermostat in there it can help roll back dump water flow at idle and keep moisture damage in check. This would be a great time for a leakdown test too .if manis are still off

The manifolds and risers are only 4 years old. EMI's. There is no sign of water leakage inside the manifolds or risers. No stains.. After each use i run my engines on a garden hose to flush out any salt water from the block and manifolds. I remember years ago I had a Gil exhaust setup on another boat and between the riser and the manifold was a piece of metal called a terbulator. This was supposed to catch and burn off any condensation from the pipes on cool down without letting the water down to the motor. Gil is the only exhaust setup i've seen this on. My EMI's don't have this. SO on cool down the condensation in dripping down into my manifolds

Possibly??

Could be but you've got me planning on pulling my sm and having a close look!