Smokeysevin's NASTY 15f build

**smokeysevin** · 06-19-2009, 03:01 PM

Edit 2/27/2020: This ski was disassembled and is currently getting a seadoo RXTX motor installed, there is still lots of interesting information in the thread and it was running as intended, thanks for reading and I hope you enjoy it. I started this build in 2009 and learned a lot in the process so please bear with Sean from 2009 as he went on this adventure.

I have purchased a non running 2005 STX-15f. The motor is not blown and I know that had I wanted to I could have gotten it running in stock form but, being the speed freak I am, I have decided to make this a potent little lake monster.

Here are the pictures, its going to take alot of work. The sponsons, nozzle, rideplate, pump shoe, and intake grate all need to be replaced because of salt rot or damage.

Sean

**smokeysevin** · 06-20-2009, 04:35 PM

Here are some pictures of the disassembled engine, as you can see the motor was neglected and the valves are heavily rusted. The cooling passages needed to be manually cleaned and blasted out with air.

Sean

**smokeysevin** · 06-20-2009, 06:56 PM

Photo of the motor removed from the hull, it can be pulled by removing the following

intake manifold
airbox
waterbox
exhaust manifold
cylinder
cylinder head

with the above removed the cases can be pulled by hand without an engine hoist

Sean

**smokeysevin** · 06-22-2009, 01:14 PM

Cylinder head torn down showing what happens when you don't flush out the ski and make sure that the waterbox is empty.

I did notice that there are holes connecting the exhaust ports from one cylinder to the next.

Sean

**smokeysevin** · 06-22-2009, 04:51 PM

I did some head work today. I smoothed out the transition from the intake side and I sharpened the divider between the 2 valves that separates the air from the intake and I knocked down the lip in the exhaust side.

The head chamber was cleaned with a scotch brite on a rotory tool and then a brass bristle wire brush. Most of the work was done to remove the salt buildup on the ports and any damage that might have happend as a result. The head has a coating on the ports which helped prevent damage but salt always wins in the end.

Sean

**smokeysevin** · 08-31-2009, 05:05 PM

This is a quick shot of what the 250x pump looks like stuffed into the 15f hull package. The rideplate, intake grate, pump shoe, and pump all fit nicely, the pump shoe needs to be bored to 155mm for the bigger pump at the front otherwise you will have water issues worth more than 3mph. The mounting face of the shoe at the rear (where the pump bolts up) is correct but the gasket that seals the pump to the shoe is too big so the sealing surface of the pump needs to be machined to the correct size.

Sean

**jp1300r** · 09-03-2009, 09:28 AM

I was kicking around the thought of going turbo on my 15F before I sold it. Here are some pictures of a turbo mocked up on a 15F engine that I found couple years ago.

**smokeysevin** · 12-09-2009, 06:05 PM

Ninja throttle set up came in today, its a slick setup, needs some adjusting though, the studs on the manifold are too long for the throttle body hoses so they hit and dont let the manifold sit flat on the head so that needs to be addressed (maybe shorter studs or cut and re thread the stock ones) The throttle bodies should fit the hull without cuts but its close, i set them on my 12f

Sensors
the throttle position sensor wont be a problem and the intake temperature sensor shouldnt be that hard, the one i am concerned about is the map sensor, I dont know what to do with it. maybe put it on the manifold before the throttles?

Fuel & Air
The other thing i need to do is get a ninja fuel rail. I also need to figure out how im going to do the filter setup on these because there isnt enough room to just stick them on the throttle bodies so i may need to get some silicon elbows and build an air box for them that hangs below...

Pictures of the cams too, they fit i looked at them wrong when i first got them.

Sean

**smokeysevin** · 03-16-2010, 04:00 PM

pictures of the wiring mods and a few other things

green 250x injectors
stock zx12r injectors
stock zx12r gear selector switch
stock zx12r wiring harness

Sean

**smokeysevin** · 03-16-2010, 04:14 PM

more pictures, you can see the trashed gauge classic 15f...

then my new gauge mounts I cut the hatch bottom off and made a plate out of lexan to mount my wideband gauge to and keep it dry (im going to seal it up anyways) and then in the factory gauge pod hole im going to mount my tach water temp and oil pressure

65# valve springs

Sean