I have a Crestliner XF189 (Aluminum Boat). Obviously I am not super concerned speed but i would like to get a little more out of it. I know I probably have a little too much weight in the back with the batteries and talons. I can get 45mph out of it but it porpoises when I do. I added a fin but I don't see a difference. I thought I would try one just to see but it hasn't helped. I may and try for lithiums one day to help lessen the weight but that will be down the road. Would lowering the motor help with this? I don't know much about this. My previous two boats were bought used and already set up for maximum performance. Just wondering.

Play with motor hight first, don't be suprised if raising the motor help. The added weight of the talons makes the transom sit deeper when running. Next option is a 4 blade prop to help with stern lift but generally will loose a few mph on top with one.

The usual cause of porpoising is the prop losing it's "bite" to the water, and it lets go. Raising the motor will typically make it worse, not better.

A few things to consider:
It's a iron boat, it's not designed to run like a fiberglass hull, it won't/can't lift because it's not designed to. So it's happy just running flatter to the water.

Aluminum hulls create a lot more disturbance in the water, your prop wants to run in clean, bubble free water, air is not your friend.

So, how do you stop the bounce?
As suggested a four blade prop is my first option, that will usually bring you into the happy zone. Powertech makes some outstanding four blades for exactly what you want.

Also as suggested, if that doesn't calm the beast, drop your motor until you find a happier place.

If THAT doesn't fix it, then you're dealing with a stubborn child and the attitude adjustment that will always cure it is some electric trim tabs.

I can get 45 but the porpoising starts at 40. Trimmed just right I am getting 38-39 without porpoising. It has a 3 blade power tech prop. Its dropped down to the next to last notch.

Rule #1 on boat setup, take it too far and bring it back. If you don't know what too low or too high is, you'll never know what just right is.

Trim tabs will work best