I have a homemade backwater clone longtail. I made it and have used it for 2 seasons. It runs a 13hp predator. I was using it on my 1648 and was getting about 10mph with me and another person. I decided to put it on my newer 1236 crestliner jon, with float pods made by backwater. I cant seem to get over 10mph. Same speed as when on my 1648. Should it not go faster on my 12 foot. Thanks

Smaller boat is prob sitting deeper in water.

With the pods, its sitting normal. i was expecting 15mph

If you're getting the same speeds on a heavier and lighter boat, may be a prop issue.
Rpm different on the different boats?

I have a 8x4 backwater prop. Same used on both boats. The only difference between the 2 boats besides size is transom height. The transom on my 1236 is An inch higher than on the 1648. I am having a little trouble with the cavitaion plate angle. It was perfect on the 1648, but now the prop is all the way in the water on the 1236. I have the backwater cav plate

The prop should be in the water. Its not a surface piercing prop. The cav plate should be just under the water and not pulling the prop down or pulling it out of the water. You'll get better speeds if the prop isn't making bubbles chopping the surface

Screen shot of a video from backwater. Notice you don't see the cav plate when on plane.
It's simple. get a mud motor. shoot ducks in the face.

Got my speed issues fixed. Once i got cav plate set right, and did a carb rejet i went from a top speed of 8mph to 17mph.

Huck is exactly right.