Haystan:
We use a Stingray Jr. on our sixteen foot jon with a 25 h.p. Mariner. Before the Stingray, with two guys in the boat, we would take water over the stern before the boat would struggle up on plane. Now the boat gets up on plane even with three big guys on board, and it holds plane at much lower speeds.
I know that my story isn't comparable to an 896 and a 175, but if the problem is horsepower to weight, a fin can help. But I would try a couple of other strategies first.
I'd look for ways to shift some of the on board weight as far forward as possible. Lighter stuff in the back storage bins and heavier stuff up front. Then I'd look at my motor height. Seems to me that your motor might be too low and needs to be raised. A jack plate can help if you don't have one, but it can be expensive. Then I'd go to trying a different prop pitch. Lower the pitch for more bite. You'll lose some top end speed, but your holeshot will be better. Maybe try a 4-blade over a three-blade.
If all else fails, consider an "SE"-style (SE3000?) hydrofoil. They're inexpensive, but you'll drill holes in the caviation plate to install it. If the cavitation plate were to break, the warranty on your outboard won't cover a replacement since you "tampered" with it.
MO