Need help

[Dustin hartle]

So I bought a bass tracker 18ft jet boat. 120hp inboard jet drive. Boat runs great except for when I run with the waves it seems like it's sucking air and revs high. Running against the waves it does amazing. No issues. I'm not sure what's going on

 

[tdonoughue]

Sounds like that are usually cavitation. Not sure of the configuration exactly on your boat, but it is possible that when running against the waves the wave action is pushing more water into the pump and you have less problem; when you are running away, that is not happening and the cavitation takes over.

I would a) check the pump for debris, b) check the intake path for obstructions, gaps, etc. and c) look at the impeller to see if it is chopped up a bit.

 

[Dustin hartle]

I've checked for debris and obstructions. And nothing. If the impeller is chopped do I have to buy new or grind it down a little ??

 

[tdonoughue]

Depends on how bad it is and what kind of damage. If it is too bad, it is new impeller time. That said, the last time I pulled mine I just had some dings on the leading edge. Took care of those with a file so they were at least smoother. It did improve my ride quite a bit.

I would not use a grinder--just a file. With a grinder you may take off so much you start to affect the balance of the impeller. You don't want to do that. If you do clean them up with a file, do try to be relatively even removing material from the different blades. Taking out a nick won't really be taking out the nick as much as making it a flat, clean gap (rather than rolled up on the edges, if that makes sense). You will just be improving it by making it smoother--not actually fixing it--and buying yourself a few years maybe.

On the bright side, the alternative is to buy a new impeller. So if you try to clean it up and mess it up, you still need to buy a new impeller. So what do you have to lose?

 

[fatboyroy]

What size wave are you talking about? Approximately what speed is it happening?

 

[Dustin hartle]

Depends on how bad it is and what kind of damage. If it is too bad, it is new impeller time. That said, the last time I pulled mine I just had some dings on the leading edge. Took care of those with a file so they were at least smoother. It did improve my ride quite a bit.

I would not use a grinder--just a file. With a grinder you may take off so much you start to affect the balance of the impeller. You don't want to do that. If you do clean them up with a file, do try to be relatively even removing material from the different blades. Taking out a nick won't really be taking out the nick as much as making it a flat, clean gap (rather than rolled up on the edges, if that makes sense). You will just be improving it by making it smoother--not actually fixing it--and buying yourself a few years maybe.

On the bright side, the alternative is to buy a new impeller. So if you try to clean it up and mess it up, you still need to buy a new impeller. So what do you have to lose?

Thanks I'll have to take a look

 

[Dustin hartle]

What size wave are you talking about? Approximately what speed is it happening?

Around 20 mph and only waves about 1 to 2 footers

 

[fatboyroy]

Try putting more weight in the back of the boat or maybe u need to calibrate jet nozzle angle.

 

[Dustin hartle]

How do I calibrate that. Or check to see if it's weong?? Sorry never worked on these before

 

[fatboyroy]

How do I calibrate that. Or check to see if it's weong?? Sorry never worked on these before

Does your boat have a trim tab?

 

[Dustin hartle]

Not that I'm aware of. Wouldn't that be on the shifter??

 

[fatboyroy]

Not that I'm aware of. Wouldn't that be on the shifter??

It’s a button that have Up and Down label or arrow

 

[Dustin hartle]

There's nothing there like that on the shifter..

 

[Dustin hartle]

Do they make anything to force more water into that cavity to stop that issue?. Or do all jet boats have this issue

 

[tdonoughue]

Well, when operating properly, no jet boats have that issue. When out of spec (either for debris caught in the intake, missing sealant, chopped up impeller, etc.), many jet boats can have the issue. It is not really a matter of forcing more water into it--much more a matter of making sure that the originally-designed path and angles are working as they should.

 

[anmut]

Think of cavitation like trying to suck through a drink through a straw with a pin hole in it. You still get some drink, but it's harder to pull up the straw because you're bringing in air with it.

Same with jet cavitation - you're injecting air into an otherwise perfect stream of high pressure water.

 

[fatboyroy]

If you go to bass tracker forums or just google bass tracker 120 jet boat, they are able to adjust trim.

 

[Julian]

Any photos of the boat? Just wonder if the position of the intake is too far forward on the hull....could be an original design flaw???