Is it possible to repair / refurbish impellers?

[Boatcrazy]

Hi all,

After reading many threads on this forum I see there are many of you that have an incredible amount of knowledge on this propulsion system.

With that being said I could use some insight. I have a 57' boat with two Kamewa Rolls royce jet drives powered by twin 1050hp engines. The rolls royce techs here in Florida replaced both impeller housings due to the issue of the vessel not reaching planning speeds. Both engines rev to max rpms but missing speed.

So fast forward, there has been an improvement since housings were replaced but I am now being told I need to replace both impellers due to clearances being too large between impellers to housings. I do understand that but am inquiring to all the knowledgeable members of this forum as to if there is anyone that repair / refurbish these impellers? Otherwise the alternative is another 15k a piece for impellers from rolls royce.

Thanks in advance for any information provided.

 

[comfisherman]

I've not used the kamewa jets but have both Hamilton and namjet. My Hamilton hasn't been rebuilt in a while but when it was a local outfit had a guy doing them who serviced the fleet of 500 or so copper river jet boats. My namjet guy does alright but is so insufferable to deal with I'd like to re jet just to deal with someone else.

I know alamarin had a big jet that had early run impellers that were not rebuildable, and ultra jet impellars are thin enough most up here swap them instead off fix(they are thin but also half the cost of Hamilton) so it's not outside the realm of possible that it's not doable.

If it were me, I'd call some Seattle or Washington area prop shops and see if they do jet rebuilds or can at least point you in that direction. Only thing we have more of in the pac nw is alloy Boats and big jets. Might be worth a try anyway.


Your not alone in sticker shock for jet parts. Three years ago gravel finally abraded my namjet to the point it needed work. Wear ring plus stator plus a rebuild on the impeller had me sketching prop conversions....

 

[Boatcrazy]

Thanks for the response. I will absolutely take your suggestion and call around the nation to some big prop shops and see if anyone has experience with or can refer me to anyone else. In the past I had to replace 3 surface drive props from a sunseeker I had and it was similarly priced for each prop, but was hoping someone might know of some shop / person that could tell me if its even plausible to repair.

Thanks again for your response and anyone else who can chime in.

 

[comfisherman]

The bay guys are funneling by around now, about 75% are jets some modern ones are getting close to your power and some certainly are. They destroy impellers in the gravel and dirt. I'll ask some when they go by if it's oem for reman or anyone third party.

 

[baeckmo]

A weld build-up of the blade tips on KameWa units is no big deal for a decent tig-welder; we do this for local commuter boats. The important thing is to use the correct filler (normally a SS 316 quality), and not overheat the material. The shape of the outer part of the leading edge is critical for cavitation performance; beware that it is not sharpened to an edge. In addition, the impeller needs a dynamic balancing due to its axial dimensions. Many prop shops only do static balancing, but that is not enough in this case. Repair shops for electrical motors often have the balancing equipment needed, if you just find a good welder.

Edit: After rereading your initial post, I am not convinced that the tip clearance is the real culprit here. You say that your're not reaching planing speed. Now if the thrust margin is so thin, that a normal wear prevents passing throu' hump speed, then something else is also "out of phase". Could you give us more info on the vessel (wl length, displacement, wl beam etc), engine type, jet unit designation?

 

[Boatcrazy]

A weld build-up of the blade tips on KameWa units is no big deal for a decent tig-welder; we do this for local commuter boats. The important thing is to use the correct filler (normally a SS 316 quality), and not overheat the material. The shape of the outer part of the leading edge is critical for cavitation performance; beware that it is not sharpened to an edge. In addition, the impeller needs a dynamic balancing due to its axial dimensions. Many prop shops only do static balancing, but that is not enough in this case. Repair shops for electrical motors often have the balancing equipment needed, if you just find a good welder.

Edit: After rereading your initial post, I am not convinced that the tip clearance is the real culprit here. You say that your're not reaching planing speed. Now if the thrust margin is so thin, that a normal wear prevents passing throu' hump speed, then something else is also "out of phase". Could you give us more info on the vessel (wl length, displacement, wl beam etc), engine type, jet unit designation?

Thank you all for the responses, it is extremely valuable and helpful. Baeckmo, thanks for the insight on the possibility of repair if that infact is my issue. Having the right outfit build back the impeller diameter with the right filler and technique is what I was hoping could possibly be an option and the information on balancing also helps me understand what would be necessary if that becomes the repair route chosen.

Here is more information on the vessel --

Dry weight: 45,500 lbs
Beam: Approx 15' 10"
Twin Kamewa FF375 HS - Direct drive
Man D2840Le403 1050hp Engines
Approx 50' at waterline