Kiwi prop size and M25xp gear reduction

[Kyle Ewing]

For those who have a Kiwi prop, what was the size and pitch you installed?  The quote I received from Kiwi is for a 15.5 x 19 prop.  They said the diameter at the tips was 1/2" greater than nominal.  Any issues with clearance?  Does the pitch match what you have and are you happy with performance?  Any lessons learned after running it for awhile?  I have a 1990 MKI with M25XP.

What is the reduction on the transmission mated to the M25XP?  I found reference to 1.79:1 but want to confirm.

Kyle Ewing
Donnybrook #1010
Chicago

[Ken Juul]

According to a couple sources the Hurth ZF5M (HBW50) is a 2.05:1 reduction

[Ron Hill]

Kyle : You should have a Hurth HBW 50 (unless a PO changed it to a HBW 100).  Both have a 2:1 reduction.
I assume that you are purchasing a 2 bladed prop??, as a 19" pitch of a 3 bladed will probably kill the engine.  There is no clearance problem with larger than a 15" diameter.  The reason for the 15" diameter is to eliminate "buffeting" from the prop wash on the bottom of the hull.   

[Kyle Ewing]

Ken and Ron,

Thanks for the correct reduction ratio.  The 15.5 diameter x 19 pitch is in degrees, equivilent to a 10 inch prop pitch.  A previous thread (http://c34.org/bbs/index.php/topic,3722.0.html) discusses prop pitch and Steve was going to repitch from the factory setting.  I'd like to know if anyone else had to adjust from factory settings.

Kyle

[Steve Sayian]

Kyle,

I bought a Kiwi last spring (3-blade).  It was pitched at 21 degrees from the factory (about 11 inches pitch).  That was way too much for my M35.  The engine smoked very bad at top end.  I had a friend dive and decrease the pitch to about 19 degrees (1 full turn on the adjustment screw).  Got better performance and picked up 400 RPMs, but the engine still smokes.  Last fall I removed the prop and re-pitched it myself to 17 degrees which is about 9.5 inches.  With the increased diameter of the blades from 15 inches to almost 16 inches, I think it will be better.  I'll be launching on May 10, so we'll see. 
Hope this helps,

Steve

[Mike Vaccaro]

Kyle,

We have a 15.5 x 19 Kiwi. 

The extra 1/2" diameter is not a problem.  The 19-degree pitch is a good starting point for an M-25 or -35 (equates to 10" pitch for this diameter wheel).  The pitch can be easily adjusted by turning set screws that limit blade travel.  1 full turn = 3 degrees of pitch, if I'm not mistaken.  This can be performed in the water. 

You'll be very pleased with the performance in reverse compared to a fixed pitch prop.  There is still a slight prop-walk, but the boat will accellerate much faster, making the rudder more effective sooner.  The caveman simple design feathers well although I've found that after securing the auxiliary in neutral, a shift to forward for 3-5 seconds followed by a shift to reverse ensures proper feathering. 

The prop requires biannual maintenance (greasing) and the blades should be painted with anti-fouling paint.  It comes with an excellent set of instructions and installation is not complicated.  Early versions of the Kiwi used bronze for hub material, but newer versions utilize 316 stainless.  We have an AQ22 SS shaft, utilize a standard shaft zinc and a Bullflex coupling.  Vibration characteristics are slightly different than the 15x9 3-blade Michigan Wheel that it replaced, and there is a distinct "clunk" as the blades transit from forward to reverse and vice versa. 

Cheers,

Mike