Small hub impellers scrap?

[Alectravis]

Are small hub impellers just scrap metal at this point?

Putting together a ski from spare parts and debating if it's even worth trying a few different small hub pitches for a 155 pump in a rocketed sj

I have always had a big hub swirl in my surf ski for the 155, but have a few random ones in my bin from part outs.

 

[fastgtfairlane]

If you already have them, no reason not to try one. They dont load the engine as hard at lower rpms as a big hub swirl type impeller so your pitch will be higher. Really comes down to engine selection. With a basic to mild "rec" 701/760, they would work fine. Dasa 1000, not so much. The big hub impellers can load the engine too hard and not allow the engine to accelerate off idle well when not pitched correctly.

 

[kevbo]

Large Hubs prevent air from lingering inside the pump. They work better and handle more power. Small hubs aren’t necessarily bad depending on conditions.

 

[Storbeck]

That might be an interesting question for the OG guys that have been around for a long time...is there anything an old school small hub impeller does BETTER than the big hub swirl impellers we're all accustomed to now?

 

[Alectravis]

If you already have them, no reason not to try one. They dont load the engine as hard at lower rpms as a big hub swirl type impeller so your pitch will be higher. Really comes down to engine selection. With a basic to mild "rec" 701/760, they would work fine. Dasa 1000, not so much. The big hub impellers can load the engine too hard and not allow the engine to accelerate off idle well when not pitched correctly.

Yeah I figured I'd end up treating them just to find out.

Large Hubs prevent air from lingering inside the pump. They work better and handle more power. Small hubs aren’t necessarily bad depending on conditions.

Yes that's the main reason I was asking, everybody is gonna go buy a large hub if you are buying a new impeller

That might be an interesting question for the OG guys that have been around for a long time...is there anything an old school small hub impeller does BETTER than the big hub swirl impellers we're all accustomed to now?

Yep, spot on to my thought process and why I came here

 

[kevbo]

That might be an interesting question for the OG guys that have been around for a long time...is there anything an old school small hub impeller does BETTER than the big hub swirl impellers we're all accustomed to now?

On a standup, no, other than already having several that are pretty good. Many years ago it was noted that you could get better radar speed with pre-large hubs. They do suffer more in rough or white water.

 

[Big Kahuna]

A prop is just part of your tuning tools. What works for 1 may not work for another... depends on applications and needs...

 

[Alectravis]

So for pitches what would you try?

(Somebody correct me if I am wrong with these)

A 144 superjet is
stock small hub 13/16
Skat mod small suggestion is a 15/19
Big hub would be around 10/15


155 for a venture and then a B2
Stock small hub 11/14. 13/16

?Mod would be maybe a 13/17 or 15/19?

Big hub swirl recommend is a 7/14, but most 701/760 guys seem to run smaller range like a 6/10



As far as I know the OEM pitches for 155 floating around are

11/14 venture/xl 701/760 65r10
13/16 Blaster 2
13/19 XL 1200 66v
16/19 Venture 1100 63m

 

[kevbo]

There is a lot of variation between brands and styles to be able to make an otherwise blind determination. I have made better use of a simple dimension between blades instead of trying to chase what is printed on the impeller itself. The manufacturers numbers are often meaningless.

 

[WFO Speedracer]

There is a lot of variation between brands and styles to be able to make an otherwise blind determination. I have made better use of a simple dimension between blades instead of trying to chase what is printed on the impeller itself. The manufacturers numbers are often meaningless.

Yep a 13/16 Skat and a 13/16 Solas won't really be comparable

 

[Storbeck]

To offer up a (basically useless because I have never tried this at all) opinion: I'd put whatever the lowest pitch one you have in there assuming it's a fairly pedestrian 7 hundred something motor.

 

[kevbo]

If its a Solas, buy the lowest pitch and be ready to bend it flatter. The Yamaha 144 YQ series work very well when pitched down.