They have multiple purposes on the ski's. They give a little bit of lift to the hull at lower speeds. They aid in handling. A side benefit is giving a swimmer (former operator) a place to grab hold and roll it back over. Usually on top of them.
They weren't real common until the early 90's. Yamaha had built the wave raider 700 and at the time, the Kawasaki 750 SS was the bad boy that everyone wanted. That wave raider had longer sponsons, and they ran slightly deeper while on slow plane. I can tell you this much. I sold the pee out of the raiders (hundreds of them) and I was commonly asked what the sponsons were for. I told most folks that they'd find out one of two ways. (1)-read up on it and (2) go to the lake, get it up to about 60mph, let off the throttle completely, turn, and then get back on the throttle quickly.....if you can stay on the ski, you're a better rider than I am. And that is the honest truth. They were hard to hold onto in a turn, they'd turn on a dime-literally. No spinout like everyone wanted. Actually I have bent handlebars on the Raider 1100's trying to hold onto them while doing a high speed turn. Sit on teh side of the seat, grab the throttle and hold on as tight as I could and still couldn't stay on the hull, found myself commonly holding onto the bars while the ski was still trying to turn, thrown to the side like a ragdoll. They were bad dudes in that department. Thank goodness I don't have to mess with them anymore!! The 2 best things about jet ski's are (1) they got rid of 2 strokes and (2) I no longer work on them, with #2 being my favorite!
I've often wondered if the duck hunters out here would benefit from the sponsons, seeing that they're many times maneuvering into/out of flooded timber, and a lot of the boat manufacturers tout their handling in such hunting waters. But then that begs the question, would a tiller operator be able to stay in the boat being that he's normally sitting atop? I know I'm certainly afraid to spin my war eagle at speed, I've never blatantly tried to turn it like that but I've come close a couple times and it don't spin out....that I know of. Can't imagine "cornering" any harder than it already does, or more specifically I can't imagine needing it to and what would happen if it did. Not my cup of tea so to speak.
But...if sponsons do indeed aid in lifting the back of the hull at low speed plane, makes me wonder if there's anyone who's tried them, just as the OP mentioned?
On the ski's, they're completely out of the water once up on plane going straight, no drag. Don't know if a typical Jon boat would be able to do that or not.
Question. I wonder if a jet outboard would benefit from sponsons more than, say, a prop outboard?
I'd be willing to try them but I ain't cutting any holes in my hull. It works fine just like it is, for what I need it for.
