Max. Prop (VIP 3 blade) variable pitch

83mm hub - standard, SAE Taper, Shaft Diameter 1 3/4", 1:16

Taper (small 1.437", max. 1.439"), Taper length 5", 1.25 thread,

width 7 threads per inch, Propeller diameter 21"

Prop Zinc Internal Hub Diameter 415 MM, 610 MM length, and 815 MM width

PYI Kevin Woodey, President; Phil, Sales; Chuck Technical; 800 523-7558

Experiences and Findings with the Max Prop

1) Used with a Yanmar 125 HP Japanese Hurth knock-off transmission as supplied by Hylas, one will need to install a Prop Brake. The good news is that Yanmar has agreed to provide this as a warranty claim and there is a promise to preinstall this device on all future Hylas 54's that come with a Yanmar 125HP (4jh3-DTE) engine.

2) There has been a massive recall by Max Prop for all VP props built when ours was provided. The adjustment retainer ring must be replaced. We sent ours in to be replaced and this prcoess will take about 3 weeks.

3) When one puts the boat in gear at low RPM's when the boat was first comissioned, a rattling noise was heard. This noise disappears at higher RPM. Max Prop indicates that this can be expected and is the result of the Damping Plate. This is unclear and will be further detailed once the prop is received back from Max Prop. Below are the findings from PYI.

Following are our findings:

1) Modified VP Mechanism: Replaced existing internal stop and added two more

Replaced existing set screw in base of hub and added two more

Replaced existing internal pin and added two more

This modification increases the strength and durability of the variable pitch mechanism and is done at no charge.

2) General Reconditioning: Balance propeller at 20 degrees

Sandblast and polish externally

Light cleanup of internals

Blades were found to be twisted so they were straightened

3) We checked the gearing mechanism and teeth and they were in great shape. We also checked to make sure the hub was sitting on the shaft properly and there was no indication that the hub was loose or wasnt sitting properly.

4)Max Prop indicates that the 2.45 : 1 transmission ratio is the proper sized ratio for a Hylas 54 with a 125HP engine and a 21 inch blade. The recommended prop pitch is 20 degrees (this appears to be one setting to high - see below). With that, our engine was able to achieve 3800 RPMs at full throttle measured at the Yanmar Tach. According to one Yamnar rep, each degree of prop pitch should provide a 7.5% increase or decrease in engine RPM depending on which way you go in adjusting the pitch. Another heuristic we were given by the Yanmar rep in Trinidad is that by increasing or decreasing the blade setting angle one notch (2 degrees) will have the corresponding impact on the engine RPM amounting to about 400 RPM / 2 degree change. The two heuristics above defy correlation. All mesurements should be done at the fly wheel to avoid errors associated with the Yanmar Tach (See next point).

5) Another finding according to the Trinidad Yanmar Rep was that the Yanmar tachometer reads about 200 RPM slower than actual speed.

6) The full throttle, no-load RPMs was adjusted 10/2002 under warranty to 4500RPMs by Trintrac.

Blade Setting Angle	RPMs Measured at Fly Wheel
20 Degrees	3640
18 Degrees	4000

Under Sail The Max-Prop Feathers to a low drag shape. Compared to a folding propeller the Max-Prop will have similar drag. The extra wetted surface of the Max-Prop blades is offset by the reduction of projected area: A.
In Forward The torque of the prop shaft acting on a "differential" type design will open the blades in unison to the preset pitch at any throttle setting. This will provide maximum efficiency (96% of same sized fixed prop) plus eliminates the vibration problems of a folding prop.
In Reverse As in forward, the torque of the shaft will rotate the blades 180 degrees in less than 3/4 of a shaft rotation, presenting the same leading edge and pitch in reverse. This provides better directional control and 80% greater power that a comparable fixed blade propeller.