Transom Bracket - twin outboards

[Fr. Frank]

Put a straight 2x4 along the hull bottom directly in front of the lower unit to see where the cavitation plate sits in relation to the hull bottom.

It's hard to tell from your photos, but if it is as it appears, I'd say you're mounted with your cavitation plates almost dead even with the hull bottom, and that's about 3 to 4 inches too low. Your cavitation problem in turns would then be (in part) a result of having your cavitation plate causing excessive turbulence from running too deep.

Use the straight 2x4 as a straight edge along the hull back to the lower unit, and, with your engines at neutral trim, put the engines where the cavitation plate is about 3" to 3 1/2" above the straight edge. That's usually a pretty good starting place.

Hopefully Peter B will chime in about where his were mounted.