Pulling my Jet pumps -- Any advice

[Ronnie]

Like many others have stated, your impellers are shot. The leading edges are dull and or rough. That pitting is caused by cavitation, I was told it is called cavitational deterioration. I just replaced the stock units in my boat with some custom pitched solas units. It takes off better / feels like it has more grip and my top speed improved by about a mile per hour (the latter is not what I expected). It was not cheap, roughly $800 for the parts, I've seen them for less than $300 each but they won't be custom pitched.

If you are on a budget check out impros in scal. They will refurb your stock units for less than $100 each but as you can imagine they are busy this time of year so I would call to ask about the bench time before Id send them there.

http://impros.com/store/index.php/services/impeller-repair.html

If you need replacements now see if anyone here is willing to sell you their stock units. I'd sell you mine cheap but we have different boats. Alternatively you can go to places like sbt or island racing for rebuilt stock or after market units. I think Carl at island racing recommends two different solas impellers (not custom pitched) to improve performance. I've also read that the engines go out of synch by a few hundred Rpms as a result of using this setup but I think this can be corrected by varying the throttles or adjusting the throttle cable lengths.

My last bit of advice on this it to have a pwc shop remove take the impellers off the shaft. It will take them less than 15 minutes and you won't have to buy any tools that may only be used one time. I found a crescent wrench big enough to fit on the stock impellers at pepboys. The solas impellers need an even bigger wrench.

Good luck.

 

[CrankyGypsy]

wow, mine weren't nearly as beat as yours - had them refurbed by SBT mid-April. $120 a pair plus tax/shipping (i dropped them off and then was too lazy, i mean busy, to go back). they did not have any in stock at that time for our boat, but took less than a week for the turnaround. i'm very happy with the way they turned out. they fit absolutely perfectly into my new OEM impeller housings. been out once since and i was getting 47 to 48.5mph on the GPS, depending on wind direction - my boat's hull could definitely be smoother and probably hasn't ever been polished, causing some drag.

 

[Port0222]

Well based on everyone saying how trashed they were and not knowing if they could be fixed, I picked up a pair of Solas on amazon with free shipping for under $200 each -- figured they were a similar price as the OEM ones new. once I get the new ones -- I may still contact SBT or Impros to get these reconditioned when they are slower to either have a back up set / or sell them.

I am looking forward to seeing how these work.

 

[Bruce]

Did you buy a different pitch for each jet?

 

[Port0222]

I did not -- Is that a mistake? Reading the forum -- I felt it was a mixed bag of people saying they need to be different (AKA what OEM is) vs the same.

Why do the stock impellers have different pitches? Is it really to even out the RPMs? My understanding is that these might have a difference of 500 RPMS or so at WOT between the 2 engines -- Thanks for bringing that up @Bruce I can always return them if I hear that this was a mistake.

Thanks!

 

[Murf'n'surf]

The different RPM is the other half of why I stayed away from Solas. You can send one out to be custom pitched to match the OEM specs.

 

[Port0222]

Do you know which side (PRT or STBD) will lag in RPMS? Why is this? Are the motors tuned differently or is the throttle position different? Can't I just adjust the Throttle position sensor?

What is the purpose of having the pitches different? one to launch and one for top end?

 

[Bruce]

I was researching impellers to try to organize a group buy last week. Unfortunately I have not found anyone wanting to sponsor it yet.

In talking to vendors I arrived at a recommendation of using YS-CD 13/19 on the starboard side and YS-CD 13/22 on the port side.

You could send the impeller(s) to GroupK or Impros for repitching.

Do you have high output engines?

 

[Bruce]

The positioning of the jets causes differing water flow to each.

You may want to consider these pump housings as well.
http://www.precisionmarinetools.com/yamaha-waverunner-pwc-replacement-jet-pump-housing-p-1.html

They are on my todo list.

 

[Port0222]

I do have the HO engines.

Thanks for the pitch recommendations. I will try these as is and see if I feel an adjustment needs to be made.
Thanks.

 

[Bruce]

I do have the HO engines.

Thanks for the pitch recommendations. I will try these as is and see if I feel an adjustment needs to be made.
Thanks.

You can order Solas impellers with those pitches from the factory. If I buy Sola impellers I will start with those.

 

[Ronnie]

Bruce is right from what I have read on the subject. The impellers spin in the same direction but one pump takes in water more efficiently than the other because of the where it is located on the hull (left or right). Ultimately running the engines at different rpms impacts tracking, especially over long distances. There isn't much difference in the pitch, 1.2 degrees, but I'm sure yamaha didn't put different impellers in just for the hell of it.

I've read a few horror strings on having to remove, repitch, reinstall, test and repeat,several times so I went with impros. The same model solas just repitched for altitude and desired performance improvement (acceleration or top speed). My tachs are still in synch throughout the throttle range but if they weren't I don't think it would be a big deal to work the throttles to balance the Rpms or just live with them a few hundred Rpms out of synch.

Incidentally, the 4th step below is to fill the cone up about 1/3rd full of grease. This is a very important page in the manual.

 

[Bruce]

The biggest issue with running impellers of the same pitch would likely be being forced to decide between running with matched output at differing RPMs so you hear the annoying "wha, wha, wha" sound or matching RPMs and having to steer to counter the unbalanced thrust.

 

[Ronnie]

Well based on everyone saying how trashed they were and not knowing if they could be fixed, I picked up a pair of Solas on amazon with free shipping for under $200 each -- figured they were a similar price as the OEM ones new. once I get the new ones -- I may still contact SBT or Impros to get these reconditioned when they are slower to either have a back up set / or sell them.

I am looking forward to seeing how these work.

Good luck with the new impellers. I'm sure that they will prove to be better than what you have now. If there is a synch problem you can always send them both or just one of them to impros to be repitched.

 

[Bruce]

@Ronnie, do you know if your impellers are Concord or Dynafly?

 

[Port0222]

Agreed -- Do you think that it is just as easy to make Throttle position adjustments in the engine compartment? @JetBoatPilot has a video on how to adjust for different RPMs to compensate for their throttle sync product. Could it be that simple instead of a repitch if there is a difference?

 

[Port0222]

Bruce is right from what I have read on the subject. The impellers spin in the same direction but one pump takes in water more efficiently than the other because of the where it is located on the hull (left or right). Ultimately running the engines at different rpms impacts tracking, especially over long distances. There isn't much difference in the pitch, 1.2 degrees, but I'm sure yamaha didn't put different impellers in just for the hell of it.

I've read a few horror strings on having to remove, repitch, reinstall, test and repeat,several times so I went with impros. The same model solas just repitched for altitude and desired performance improvement (acceleration or top speed). My tachs are still in synch throughout the throttle range but if they weren't I don't think it would be a big deal to work the throttles to balance the Rpms or just live with them a few hundred Rpms out of synch.

Incidentally, the 4th step below is to fill the cone up about 1/3rd full of grease. This is a very important page in the manual.
View attachment 22593

@Bruce -- Is there an online version of that service manual anywhere?

 

[Bruce]

I believe you are going to want to repitch at least one of the impellers or order impellers with differing pitch. If you are up for experimenting I will be excited to hear how you do with matched impellers.

 

[CrankyGypsy]

the differing pitches are due to the angle of the hull off the keel. the rotation direction of the impellers is the same, but the starboard side has a steeper flow of water, causing more thrust ...if I'm understanding that correctly. hence the difference in pitch to equalize RPMs.

https://jetboaters.net/threads/informative-read-on-jetboat-cavitation-pump-load-and-prop-slip.5557/

 

[Ryan Vogels]

Don't adjust the throttle position sensor. You could cause all kinds of hard by doings so. Even little things could pop up.... no wake mode not working as an example. You should really look at the impeller from the back side as well. There should not be much room between the impeller and the wear ring.