650/X-2 js550 w/650 swap impeller search?

[mike b]

I installed a stock 650 motor and everything on the ski is stock except a 750 carb with fuel pump attached because my 650 carb took a dump. So basically my motor is still stock 650 power but in a 550 hull. The hull is an 85 if that identifies the pump but what impeller should i use. took to the lake today and pretty much cavitation all day. Revs up and no movement really. Is that expected without changing impellers or should i be looking at other issues? and what pitch impeller should i look for. Saw people using and 18* but that motor seemed to have upgrades

 

[yamijumpn]

i think i used a 14/19 or something like that when i did the swap in mine 7 years ago. since you have that much more power now you will hav to make sure the pump setup is in near perfect condition. pull it check the vanes for large chips etc. Whatever impeller you get verify the impeller to housing side wall clearance. a larger than desired gap here will cause cavitation. and then make sure its sealed to the hull good so it cant suck air from around the top/sides of the pump. might consider a scoop grate as well to feed that pump as well.

The theory is simular to someone who puts a ton of engine mods into a car but cant launch it without getting massive tire spin. gotta get the power to the ground or in this case the water.

 

[mike b]

yeah when i tried it yesterday it felt like a burnout hah. motor sounds fine but cavitation of some sort or damaged pump. Felt like a superjet with busted pump seal where it just wouldn't move. will pull the pump today and see

 

[yamijumpn]

once its out get in the tunnel. scrap all the old sealing material off so when you stick it back in your can seal it up good. i forgot the pump shoe was part of the pump on those skies until this thread.

 

[Big Kahuna]

Yup. If you ran a straight 15 degree. Your going to have to step it up to 17 or 18. Or comparable Variable pitch. 14-19 or 15-20. But guessing on those.

 

[bored&stroked]

Most people go with 18-20*.

 

[mike b]

I took off the old stock prop. It's a good thing I had to cut that prop off because it was KO'd. I believe I out on a skat17. Something someone nearby gave me and the ski was able to pull me up. Fighting cooling issues I did not test the ski much but know it falls short of my superjet but at least now it's a reliable 550, something factory could not say lol

 

[yamijumpn]

now pipe it!

 

[mike b]

Fighting some cooling issues but think I will have that taken care of quite soon. Doing some cosmetic things to the ski and have to silicone in the pump section. Hopefully there is some cavitation because it is gutless on the bottom end lol. Then again hopping off a SJ or AM ski everything feels slacking on the bottom end. Have to adjust steering because turning right is kinda hard but left is super sharp. I kinda like the ski after it plains out tho.