Any Jet Boat experts on the forum ?

[scottrods]

Sometimes you can extend the jet out the back of the transom to push the extra stage out without changing the engine position.

You said "it's worth spending 100's on, not 1000's" - LOL. It's a BOAT - a hole in the water you pour money into.

[baldbob]

Interesting that a course impeler dont work and only does 3200 rpm!! What revs does urs do WOT mine does 4800!!!

[veitnamcam]

Impeller pitch is like changing gearing, obviously it is to high for the standard combo(the coarse) but could be ideal if the nozzle has been bored there by reducing pressure Ie you have to pump more to get same pressure.
Interesting you can only get 3 pitches, for the ski there was a almost endless variation of straight and progressive pitch and even variations in the progression from front to back of impeller in the progressives.

[Happy]

Impeller pitch is like changing gearing, obviously it is to high for the standard combo(the coarse) but could be ideal if the nozzle has been bored there by reducing pressure Ie you have to pump more to get same pressure.
Interesting you can only get 3 pitches, for the ski there was a almost endless variation of straight and progressive pitch and even variations in the progression from front to back of impeller in the progressives.

Umm it's 40 yrs old That's the problem no one thought we d be still using them or they'd last that long There were only three choices back in day dot. It's ok just is what it is

Do you reckon I could enlarge the out hole and it may help Be like porting my old BB Chev heads took hours but got there in the end

[veitnamcam]

No.

Tuiman alluded to the nozzle already being enlarged witch combined with any impeller/wear ring damage or wear is not building enough pressure behind the impeller to load the motor, hence lots of revs no go.

A larger nozzel and more flow will (generalizing here) get you out of the hole quicker providing you are still loading the motor IE using all the available horsepower but drop top speed as max pressure pumped will be lower with an impeller that was optimum pitch beforehand.

From your symptoms this could be a large part of your problem.

Trimming it down (with the wedge) will get you out of the hole quicker and make it turn better with less slide, But once up on the plane it will drop your top speed.

But your main problem is loading the motor, new wear ring and rebuilt or new impeller and perhaps sleeving the nozzle back down.
There are propeller heads out there who can mod/re pitch impellers

You need to get it out on flat water and up on the plane give it WOT and see what revs it will pull.

[Happy]

Ok so have the wedge comin. Was gonna fit and try first any way so will trial and full throttle see what happens Record details and post them. Don't forget tho that the supposed guru of these has said don't throw money at as been there done that. Get a two stage trouble is they re expensive and the boats not that great so maybe move on ?

[Spanners]

Take note of max rpm under WOT

[ishoot10s]

a hole in the water you pour money into.

Yep, may as well stand under a cold shower rippin' up hundies...