OUTLAW EAGLE MANUFACTURING

Polarkiwis · Joined: 22 Feb 2006 Posts: 24

SJ 175hp 3blade vs 4blade impellor speed performance?

Anyone had any experience? What is faster for racing? I have been entering R2 class here in NZ. My boat has been going about 80kmh with the 4 blade from a SJ 240hp unit. Reving at 5200rpm with a new SS wear ring and overhauled impellor. Thinking about buying a 3 blade if it adds a some extra kmh. (this is the factory impellor for a SJ175hp.)

I put the 4 blade in about 100 hours ago. At the time the three blade was eroded and OD's needed doing. Also changed grills from homemade to factory mercury stainless stone grill. So this was a vast improvement in hole shot, turning etc.

Any comments from any one who has experimented?

We managed to come 8th out of 21 with the slowest boat. This race was on the braided Waimakariri River in NZ last weekend. Was heaps of fun.

Posted some photos for you. We are 11R

Cheers
Brian

Polarkiwis · Joined: 22 Feb 2006 Posts: 24

Alumaman · Joined: 26 Jul 2005 Posts: 306 Location: Whitecourt

Your doing good with a 175 HP SJ. R class has a 100 kph maximum ??? is that right. Driver skill and navigation over speed.

My experience; the three blade is faster (maybe by 1 kph), but the four blade will give better hole shots. And the high skew, it will be the slowest of the three but loves to pump gravel. Keep clearances low, .020 to .030 is best.

Polarkiwis · Joined: 22 Feb 2006 Posts: 24

In NZ R2 is 65-90kmh and R1 is 90-105kmh. It is for 'Family boats'

We do about 80kmh GPS'ed on a lake.

If it was an extra 3-5kmh would be worth getting a three blade impellor

Polarkiwis · Joined: 22 Feb 2006 Posts: 24

Someone must have this knowledge or info? Question

RaceFan · Joined: 18 Jul 2006 Posts: 34 Location: Peace River

All the Canucks are too busy digging out of all the snow! Mad

Alumaman · Joined: 26 Jul 2005 Posts: 306 Location: Whitecourt

Any chance you could borrow a three blade and try it out in your boat? The 175 was designed to run a 3 blade so theoretically it should be faster. You may have given up some top end with the 4 blade. I'm guessing that there is only a 1 to 2 km/h difference between them.

Clark · Joined: 17 Jun 2005 Posts: 20 Location: Cotton Tree

Just buy the 240 and be done... we could get on the podium with the extra 15 kph! Very Happy

Plus I promise I will reduce to 3 pies a day.

Polarkiwis · Joined: 22 Feb 2006 Posts: 24

Tested during race conditions. Aboth about the same at top speed or possibly 1kmh slower. Hard to gauge. Last month I ran the race with a 4 blade reconditioned and OD's done it did 88.6 kmh downstream on the Waimakariri max. This race down the same river in similar conditions with the 3 blade and I did 87.6kmh max. About an extra 50-100rpm

Still had a blast racing in R2 class this past weekend. Our rivers on the 1st day were super low and braided. Went for a few massive shingle slides where fibreglass got us through.

See here for more race reports and photo's:

http://www.nzjetboating.com/yabbse/index.php?topic=8960.0