RECENT SUPER CHICKEN BUILD CAVITATION ISSUE

Joined
Dec 6, 2010
Likes
4
Location
NH
#1
short verison
13/18 prop cavitates down low, slow acceleration, and slow up top (not max rpm)

long version
i saved a 750 BP motor, lightened flywheel, B pipe (center bleed style), dual kehin carbs, 750 ebox, and pump (with 13/18 KA-SC-I Solas, AM cone, and some sort of reduction nozzle spacer/extender, plastic steering nozzle) from a jet mate that was extremely fast IMO. neck snapper, crisp throttle and hook up everywhere

i sold the jetmate as an empty hull and kept all the above to maybe put into my keeper jetmate that has a nicer hull. since it already had a 750 small pin, i never did the swap and it sat in a bin for a year.

i came across the SC empty hull and figured i could throw it all in there. thinking if it ran anything like that jetmate it would be a silly fun ski..
I swapped the dual kehins for an sbn46 . and I swapped the B pipe for a coffmans pipe and manifold. i used a sea doo purple waterbox and a scoop intake grate (jet mate used stock waterbox, and i forget which intake grate it had). oh and i also added dual cooling to the pump before it went in the SC.

i get coffee brown plugs at both high and low plug chops new 2.0 needle/seat and black spring. jetting was something around 120/147.5 i think (i have it written down if i need to verify)

when i gas it off idle it will cavitate and rev up really high until i let off the gas (motor sounds awesome when it does this). if i gas it off idle while turning slightly it will hook up and take off slowly, and get on plane after a circle, maybe 2. if i remove the intake grate, this cavitation stops and i can easily get on plane, however still WAY slower than it should be.

once on plane, acceleration is doggish. top speed is slow and not max rpm.

i cant figure out what changed. i believe if the jet mate pushed that prop, then it should be even easier for the SC...

i siliconed the pump in, and have successfully done this before without this issue

i tried impros and they said they were at a loss. that i could try the 10/16 hooker but they couldnt guarantee it would be the issue.

the pump is a little salty but like i said... this exact setup (minus pipe and carbs) RIPPED in the jetmate.

desperate for a solution soon. been building it for a painful 6 months due to other projects in the way. hoping to get it done soon. i may pull the pump this weekend to inspect, but i cant imagine im going to find an issue...
 

Attachments

Big Kahuna

Administrator
Joined
Jan 14, 2006
Likes
6,053
Location
Tuscaloosa, AL
#2
you are either sucking air from the pump or from where the driveshaft comes through the carrier housing at the hull. Pull pump, clean up all silicone and re-seal it back up.... then test.
 

Ducky J. Trump

Trump 2020
Site Supporter
Joined
May 13, 2012
Likes
4,022
Location
Charlotte, NC
#3
I would also consider trying the stock exit nozzle/reverse bucket combo, just to rule out the nozzle causing you some issues for some reason.
 
Joined
Jul 3, 2018
Likes
3
Location
seattle
#7
Have a stock (except stainless 16 impeller) SC that does exactly the same.
It would have to be the silicone at the pump perimeter, and greasing the driveshaft point at the bearing housing.(plus silicone at the bulkhead)
The air is getting in there somehow. Mine needs reseal too & I need to veer left to get it to hook up. : (
 
Top Bottom