WEE Boats - Engines Jet Unit Tech info

[vyrus-jet]

start from scratch, jetski ones are normally glass and part of the hull , or in the case of the yamaha cast alloy and very crappy/thin and prone to cracking

[Fuges]

Hi All, got my 3m/900cc kawasaki boat in the water for the first time this morning, went pretty good top end but seems to cavitate quite a bit out of the hole and when cornering.
The intake i built is 400mmx150mm with 6mm bars and around 8mm gaps (is this to tight?)
Has near new impellor and wear ring.
I also have not put any planning strakes on yet, do these help at all with cavitation?

[Matthewf/Norbert/TuiDog]

have you put urethane around the grill to stop air?

depending on design/luck of the grill, it may suck air in any case

[Fuges]

have you put urethane around the grill to stop air?

depending on design/luck of the grill, it may suck air in any case

Urethane around the grill?? is this to smooth the lead into the unit?
Have a sheet of polyethylene on the bottom and have shaped that into the unit.

[Matthewf/Norbert/TuiDog]

to stop air bleeding around grill edges

[Fuges]

to stop air bleeding around grill edges

Cheers got it sorted, the unit is welded in so wasnt leaking there, was leaking through the rubber seal on the bearing housing, all sealed up now and will have another run tomorrow.

[jeremy williams]

What type of steering set up are you guys using? A rack and pinion type? Thanks

[Karl]

http://www.google.com/patents/US8070538

Patent describing why the 155mm kawasaki pumps have the notched stator

[Paul]

http://www.google.com/patents/US8070538

Patent describing why the 155mm kawasaki pumps have the notched stator

Nice find Karl.

So in summary, a limitation of the casting process, means they can't cast the high rake they would like (to reduce cavitation), at the outer of the leading edge of the stator vanes.  As they can't get the angle they want, the compromise is to remove leading edge metal, to get a greater distance between blade rear-edge and stator leading-edge, near the edge of the pump.

Are these castings die-cast or sand-cast?  My memory would say die-cast (they're fairly smooth), wheras the bigger units (e.g. Hamilton) are sand-cast.  Sand casting doesn't have this die-casting limitation, of needing to be able to remove the finished casting with the die still intact.  With sand casting the sand form is broken, allowing _any_ shape out, thus not a problem getting the stator vanes any shape needed with sand casting.

[Matthewf/Norbert/TuiDog]

im guessing the extra area at the the od gives room/lower pressure for expansion preventing boiling/cavitation

[Karl]

After reading the article it wasn't clear to me why wouldn't you just space the impeller further forward? I.e bigger gap between the back of the impeller and the front of the stator.

[Matthewf/Norbert/TuiDog]

i think they are trying to reduce cav and increase efficiency at the OD high speeds whilst having tight clearance on the rest of the blade. maybe they are chasing the last fraction or mph....

[Paul]

After reading the article it wasn't clear to me why wouldn't you just space the impeller further forward? I.e bigger gap between the back of the impeller and the front of the stator.

to reduce pressure loss by minimizing a distance between the impeller ... and the fairing vanes

[Dicko]

The wear ring on my 15f has reached it's use by date, has anyone changed a wear ring on a 15f and was it difficult?
I can get a reconditioned stator with new bearings and a shaft for $400, but the bearings and shaft are fine, don't really want to fork out that kind of money, if I can change the wear ring, especially as it is going to be an ongoing problem.

I've checked out Youtube, it seems to have every other type of unit except the 15f.

[heemi.v8]

http://www.pwctoday.com/showthread.php?t=136633

i find this hard to believe but these guys reckon you have to replace the whole thing...


on the seadoos you just put the stator in the freezer and the plastic liner pops out. then put the new liner in the freezer and it will push in by hand. if your on the river you can use a hammer and chisel carefully. this method requires the impeller to be removed.