That's pretty impressive!! This is the first one I have seen where someone actually fabricated their own impeller duct (scoop) I bet that was a PITA!
Most people just hack the glass hull out of the ski and splice it into the boat (which, IMO, is a substandard design) When I built mine, I used a pump from a Yamaha XL1200.
I think the 1200 and the XL700 are the only pumps which use a bolt in aluminum scoop. All the other ones are part of the fiberglass hull, with threaded inserts on the back end, where the impeller vane/wear ring bolt up to it.
Pretty impressive throttle cable actuator, too! For mine, I took an easier route, and used a simple lever with a pivot point, and attached the cable directly to that, using a ball end fitting for the cable so it could pivot within a notch cut out in the lever.
Anyhow, my boat started out as a 1997 DuraCraft 1648SV which someone nearly killed by painting it with copper paint and leaving it in salt water. I repaired the damage, a lot of it being on the center V of the hull, and then gave it a new lease on life by turning it into a jetboat. The first time with a 1998 Tigershark 1000 cc engine.
And this past summer, I put a Yamaha MR-1 engine in it....it's 160+ HP at 10K RPM's, as well as being a 4 stroke. So far, I'm loving the new engine. MUCH more power than the old TS1000.
My original inspiration for the idea came from the fact that I owned a Sea Doo Speedster jetboat (it had twin engines, just like the one you used in your boat, the 717 Rotax) It was a cool little boat, but it couldn't go in really shallow water, and that's what I wanted. And like the Sea Doo Speedster, my boat also incorporates the use of a 'stomp grate' on the pump intake, for clearing weeds or other debris.
Again, nice work, and I'm sure you will really enjoy being on the water with your project boat. I know I have enjoyed mine for the past 6 years. I've had more fun with this boat that any other boat I've owned.[youtube]ALUMA JET STUNT VIDEO[/youtube]