^^might be right. too much weight. In your case, though, dropping the leg to about the level of that second plate (AV plate about an inch below bottom of the hull, guessing from pic), you might have more trim adjustment available without porpoising. Sage advice is usually to raise it, so might be counterintuitive....
(edit: mounting height issues aside, transom angle might be a factor. thinking matching the motor trim angle with the transom angle might be a better starting point, then adjusting trim angle for performance. Depending on your hull, that starting trim angle might be the optimum operating angle too. Also not orthodoxy, as outboards are typically mounted with the AV plate on the same plane as the boat bottom, regardless of or in spite of transom angle -- older Whalers, for example. I've sometimes found on my old hulls that hull characteristics, loading/balance, etc. can change that -- maybe motor weight too, in your case. )
