Jetstream Cavitation Help PLEASE

mjpcarbon
Posts: 2
Joined: 22 Jul 2021, 16:52
Location: fairfield new jersey

Jetstream Cavitation Help PLEASE

Post by mjpcarbon »

So here is the long story so far.
Recently finished building a JetStream Headwater 10' aluminum boat. Powered by an 04 RXP engine.
The problem Im having and lost nearly all my hair is the boat accelerates great lots of power til about 5500 rpm @30 ish mph. Anything after that just overrevs the engine.
Things Ive done:
Ceramic Ring and boot New properly sealing and aligned.
ReSealed the pump housing for the 3rd time
Prop in excellent condition and New wear Ring

Setup is as follows and is possible cause.
Nozzle is trimmed all the way down, other wise the boat porpoises badly
Nozzle is about 3" above the bottom of the keel line

Is it possible the trim is the root of my problem lifting the ass of the boat, and if so how would I then cure the dolphin bouncing that I believe would result if it were trimmed upward

CedarRiverScooter
Posts: 1505
Joined: 13 Nov 2014, 08:01
6

Jetstream Cavitation Help PLEASE

Post by CedarRiverScooter »

A picture of your boat would be helpful. It sounds cool.

I have a JetJon & also had porpoising issue.
After many ideas, I finally got it under control.
I got a pump 'wedge' plate & installed it upside down. They normally are used to push the bow higher, opposite my goal.
I also made a trim tab that attached directly to the trailing edge of the ride plate. It is 1/8 aluminium & has about 2 inches of overhang. I just kept bending it further down until the porpoising stopped.

There also is a special intake grate, called a top-loader, that may help if your getting air in intake.. Be advised those will let flotsam in & jam your pump. Been there.

mjpcarbon
Posts: 2
Joined: 22 Jul 2021, 16:52
Location: fairfield new jersey

Jetstream Cavitation Help PLEASE

Post by mjpcarbon »

Do you think the cavitation is being caused because I have to much nose down trim and it is lifting the back of the boat ?

CedarRiverScooter
Posts: 1505
Joined: 13 Nov 2014, 08:01
6

Jetstream Cavitation Help PLEASE

Post by CedarRiverScooter »

No, bow down should provide clean water

Is the cavitation (more likely ventilation) worse when you go over chop or wakes?

Have you measured the clearance impeller to wear ring? Needs to be less than .01 inch. I read you put in new ring but ya never know.

Another source of air could be shaft bearing, but this is unlikely.

You may need to put in a spoon. Lots of threads on those here from member Ranchero.